Tutorial

Launch Japanese Store: Localize Prices with Rounding

Published June 2, 2026

Launch Japanese Store: Localize Prices with Rounding

Launching Your Japanese E‑Commerce Store with SiteLocaleAI

Expanding an online store into Japan opens a massive market, but success hinges on more than just translating text. Japanese shoppers expect prices that feel right—prices ending in 99 ¥, 98 ¥, or 95 ¥ are perceived as better deals. SiteLocaleAI makes this easy with a drop‑in JavaScript library, self‑hosted LLM translation, and built‑in psychological rounding for price localization.

1. Install the Library (Framework‑Agnostic)

SiteLocaleAI works with any front‑end framework—React, Vue, plain HTML, or even a Shopify theme. First, add the library via npm or a CDN script tag.

npm install @sitelocaleai/core

Or, for a quick start without a build step:

<script src="https://cdn.sitelocaleai.com/v1/sitelocaleai.min.js"></script>

Tip: If you’re on WordPress, the official plugin handles the script injection automatically—no Node.js required.

2. Configure Your LLM API Keys

SiteLocaleAI is self‑hosted, meaning you provide your own LLM credentials (Claude, GPT‑4o‑mini, etc.). Store the key securely on your server and expose it via an environment variable.

// src/config.js
export const LLM_API_KEY = process.env.LLM_API_KEY; // e.g., Claude API key

Pass the key when initializing the client:

import { SiteLocale } from '@sitelocaleai/core';
import { LLM_API_KEY } from './config';

const locale = new SiteLocale({
  apiKey: LLM_API_KEY,
  targetLang: 'ja', // Japanese
  // optional: custom prompt for tone/style
});

3. Price Localization with Psychological Rounding

3.1. Why “Charm” Rounding?

Psychological pricing (aka charm pricing) leverages the left‑most digit to make a price appear lower. In Japan, the most common endings are ¥99, ¥98, ¥95, and ¥90. SiteLocaleAI’s priceLocalizer module automates this.

3.2. Set Up the Rounding Rules

// src/price.js
export const roundingRules = {
  // Convert from USD to JPY using a live rate (you can pull from an API)
  conversionRate: 150, // example: 1 USD = 150 JPY
  // Desired endings per currency
  endings: [99, 98, 95, 90],
};

3.3. Apply the Rounding Function

import { priceLocalizer } from '@sitelocaleai/core';
import { roundingRules } from './price';

function localizePrice(usdAmount) {
  const rawJpy = usdAmount * roundingRules.conversionRate;
  // priceLocalizer rounds to the nearest allowed ending
  return priceLocalizer.roundToEnding(rawJpy, roundingRules.endings);
}

// Example usage
const priceTag = document.querySelector('.price-usd');
const usd = parseFloat(priceTag.dataset.usd); // e.g., data-usd="49.99"
const jpy = localizePrice(usd);
priceTag.textContent = `¥${jpy.toLocaleString('ja-JP')}`;

The roundToEnding method works like this:

  1. Divide the raw JPY amount by 10 to isolate the last digit.
  2. Find the nearest allowed ending from the endings array.
  3. Replace the last two digits with that ending, preserving the higher‑order digits.

Result: $49.99 → ¥7,500 (rounded to the nearest ¥99 ending).

4. Translate Page Content on the Fly

SiteLocaleAI can translate any DOM element using the LLM. Wrap translatable text in a data-locale attribute.

<h1 data-locale="title">Welcome to Our Store</h1>
<p data-locale="description">Free shipping on orders over $50.</p>

Then call the translation method after the page loads:

locale.translatePage().then(() => {
  console.log('Japanese translation complete');
});

For large catalogs, consider pre‑rendering translations with the CLI (see step 5).

5. SEO‑Friendly Pre‑Rendering for Search Engines

Search engines struggle with client‑side translations. SiteLocaleAI’s CLI can generate static HTML snapshots for each language, ensuring Google and Yahoo index the Japanese version.

npx @sitelocaleai/cli prerender \
  --src ./public \
  --out ./public/ja \
  --lang ja \
  --api-key $LLM_API_KEY

The generated /ja folder contains fully translated pages with localized prices, ready to be served via a language‑specific route (example.com/ja/).

Add a <link rel="alternate" hreflang="ja" href="https://example.com/ja/" /> tag to your <head> for proper language targeting.

6. WordPress Plugin (No Node Required)

If your store runs on WordPress, install the SiteLocaleAI plugin from the marketplace. After activation:
1. Add your LLM API key in the Settings page.
2. Enable “Price Localization” and set the conversion rate.
3. The plugin automatically injects the translation script and replaces price shortcodes with the rounded JPY value.

No additional code is needed—perfect for non‑technical store owners.

7. Test & Deploy

  1. Local testing – Use the browser console to verify price rounding and translation.
  2. A/B testing – Serve the original English version to a control group and the Japanese localized version to a test group. Measure conversion lift.
  3. Analytics – Track price_jpy events in your analytics platform to monitor pricing performance.

8. Wrap‑Up

By combining SiteLocaleAI’s self‑hosted LLM translation, psychological price rounding, and SEO pre‑rendering, you can launch a Japanese storefront that feels native, builds trust, and ranks well in local search.

Ready to go global? Try SiteLocaleAI today and watch your international sales grow.

Further Reading

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