I want to include the VAT in the price of a line item. My solution is to: Set the price of the item to its actual price ($2990) divided by 1.06. Add an object to the "taxes" array and set its rate to 6. import { invoices } from 'wix-billing-backend'; export function create() { invoices.createInvoice({ ... lineItems: [{ id: '0', name: "Line Item", quantity: 1, price: 2990 / 1.06, taxes: [{ name: "VAT", rate: 6, code "VAT" }] }] }); This works sometimes, with some prices. However, in this case, I get this error: balance USD -0.01 must be non negative How do I approach rounding in Velo and JS?