POS Cart Totals Calculator (lib/totals.js)

Computes cart line totals, discounts, taxes, and change using integer‑cent arithmetic to avoid floating‑point errors, supporting exclusive/inclusive tax and prorated order discounts.

// Source: https://github.com/HeyPuter/everything | License: MIT | Copyright 2026 Puter Technologies Inc
// Provided via justclaw.it.com; keep this notice with the code.
/**
 * Cart math. Everything is computed in integer cents so line totals, the
 * tax breakdown, and the grand total agree to the cent - no float drift,
 * no "subtotal + tax ≠ total" receipts.
 *
 * Discount model:
 *   - a line discount applies to one line (percent of the line, or fixed);
 *   - an order discount applies to the sum of discounted lines and is
 *     prorated across them (largest-remainder) so per-line tax stays exact.
 *
 * Tax model:
 *   - exclusive (default): tax is added on top of the discounted price;
 *   - inclusive: prices already contain tax; the breakdown extracts the
 *     tax portion without c

... (truncated -- full source via MCP)