Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$32.62	4.371%	$34.0458	$34.05	$34.05	$34.00
Purchase #2	$115.44	3.334%	$119.2888	$119.29	$119.30	$119.30
Purchase #3	$53.62	10.678%	$59.3455	$59.35	$59.35	$59.30
Purchase #4	$178.73	7.676%	$192.4493	$192.45	$192.45	$192.40
Purchase #5	$145.54	3.428%	$150.5291	$150.53	$150.55	$150.50
Purchase #6	$10.84	5.783%	$11.4669	$11.47	$11.45	$11.50
Purchase #7	$141.30	10.785%	$156.5392	$156.54	$156.55	$156.50
7 purchase totals =	$678.09		$723.6646	$723.68	$723.70	$723.50