Why is BigInt generally the wrong tool for representing monetary amounts with decimals, like $19.99?

BigInt only represents whole integers — it has no concept of a decimal point. The common workaround is to store money as an integer count of the smallest currency unit (e.g. cents) rather than trying to represent fractional dollars directly, whether using BigInt or regular Numbers.

// Store cents as an integer instead of dollars as a float
const priceInCents = 1999; // represents $19.99
const total = priceInCents * quantity; // exact integer math, no float errors