roundTo method
Rounds this number to fractionDigits decimal places.
Implementation
double roundTo([int fractionDigits = 0]) {
if (fractionDigits < 0) {
throw RangeError.value(
fractionDigits, 'fractionDigits', 'must not be negative');
}
final mod = math.pow(10, fractionDigits).toDouble();
return (this * mod).round() / mod;
}