Precise rounding of numbers

round-precise.js

function round_precise(value, exp) {
	if (typeof exp === 'undefined' || +exp === 0)
		return Math.round(value);

	value = +value;
	exp  = +exp;

	if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0))
		return NaN;

	// Shift
	value = value.toString().split('e');
	value = Math.round(+(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp)));

	// Shift back
	value = value.toString().split('e');
	return +(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp));
}