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	$232.67	8.733%	$252.9891	$252.99	$253.00	$253.00
Purchase #2	$146.41	6.236%	$155.5401	$155.54	$155.55	$155.50
Purchase #3	$195.95	13.834%	$223.0577	$223.06	$223.05	$223.10
Purchase #4	$157.64	9.699%	$172.9295	$172.93	$172.95	$172.90
Purchase #5	$125.95	4.276%	$131.3356	$131.34	$131.35	$131.30
Purchase #6	$72.51	8.829%	$78.9119	$78.91	$78.90	$78.90
Purchase #7	$153.88	7.467%	$165.3702	$165.37	$165.35	$165.40
7 purchase totals =	$1,085.01		$1,180.1341	$1,180.14	$1,180.15	$1,180.10