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	$222.51	13.488%	$252.5221	$252.52	$252.50	$252.50
Purchase #2	$237.81	10.411%	$262.5684	$262.57	$262.55	$262.60
Purchase #3	$43.86	10.635%	$48.5245	$48.52	$48.50	$48.50
Purchase #4	$64.60	9.137%	$70.5025	$70.50	$70.50	$70.50
Purchase #5	$34.41	6.357%	$36.5974	$36.60	$36.60	$36.60
Purchase #6	$176.48	13.428%	$200.1777	$200.18	$200.20	$200.20
Purchase #7	$77.29	5.595%	$81.6144	$81.61	$81.60	$81.60
7 purchase totals =	$856.96		$952.5070	$952.50	$952.45	$952.50