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	$235.82	3.733%	$244.6232	$244.62	$244.60	$244.60
Purchase #2	$71.78	3.747%	$74.4696	$74.47	$74.45	$74.50
Purchase #3	$60.78	10.425%	$67.1163	$67.12	$67.10	$67.10
Purchase #4	$72.80	12.636%	$81.999	$82.00	$82.00	$82.00
Purchase #5	$90.51	3.332%	$93.5258	$93.53	$93.55	$93.50
Purchase #6	$120.31	5.206%	$126.5733	$126.57	$126.55	$126.60
Purchase #7	$48.83	3.427%	$50.5034	$50.50	$50.50	$50.50
7 purchase totals =	$700.83		$738.8106	$738.81	$738.75	$738.80