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	$74.60	10.811%	$82.665	$82.67	$82.65	$82.70
Purchase #2	$167.64	13.634%	$190.496	$190.50	$190.50	$190.50
Purchase #3	$53.76	3.677%	$55.7368	$55.74	$55.75	$55.70
Purchase #4	$105.42	6.193%	$111.9487	$111.95	$111.95	$111.90
Purchase #5	$30.88	11.503%	$34.4321	$34.43	$34.45	$34.40
Purchase #6	$138.66	11.189%	$154.1747	$154.17	$154.15	$154.20
Purchase #7	$41.36	10.490%	$45.6987	$45.70	$45.70	$45.70
7 purchase totals =	$612.32		$675.1520	$675.16	$675.15	$675.10