In Java currency is usually stored in BigDecimal. But what to use to store currency values in Dart? BigInt doesn't seem to be a solution because it is for integer values only.
Definitely do not use doubles for an accounting application. Binary floating point numbers inherently cannot represent exact decimal values, which can lead to inaccurate calculations for seemingly trivial operations. Even though the errors will be small, they can eventually accumulate into larger errors. Setting decimal precision on binary numbers doesn't really make sense.
For currency, you instead either should something intended to store decimal values (e.g. package:decimal) or should use fixed-point arithmetic to store cents (or whatever the smallest amount of currency is that you want to track). For example, instead of using doubles to store values such as $1.23, use ints to store amounts in the smallest unit of currency (e.g. 123 cents). Then you can use helper classes to format the amounts wherever they're displayed. For example:
class Money {
int cents;
Money({required this.cents});
@override
String toString() => (cents / 100).toStringAsFixed(2);
Money operator +(Money other) => Money(cents: cents + other.cents);
// Add other operations as desired.
}