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	$40.71	13.349%	$46.1444	$46.14	$46.15	$46.10
Purchase #2	$95.47	5.717%	$100.928	$100.93	$100.95	$100.90
Purchase #3	$193.28	12.335%	$217.1211	$217.12	$217.10	$217.10
Purchase #4	$151.52	12.300%	$170.157	$170.16	$170.15	$170.20
Purchase #5	$117.29	6.807%	$125.2739	$125.27	$125.25	$125.30
Purchase #6	$156.82	7.540%	$168.6442	$168.64	$168.65	$168.60
Purchase #7	$24.84	13.737%	$28.2523	$28.25	$28.25	$28.30
7 purchase totals =	$779.93		$856.5209	$856.51	$856.50	$856.50