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	$179.80	7.664%	$193.5799	$193.58	$193.60	$193.60
Purchase #2	$102.77	8.234%	$111.2321	$111.23	$111.25	$111.20
Purchase #3	$177.66	10.735%	$196.7318	$196.73	$196.75	$196.70
Purchase #4	$203.73	4.363%	$212.6187	$212.62	$212.60	$212.60
Purchase #5	$157.35	8.198%	$170.2496	$170.25	$170.25	$170.20
Purchase #6	$50.59	9.753%	$55.524	$55.52	$55.50	$55.50
Purchase #7	$146.48	3.547%	$151.6756	$151.68	$151.70	$151.70
7 purchase totals =	$1,018.38		$1,091.6117	$1,091.61	$1,091.65	$1,091.50