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	$114.95	8.283%	$124.4713	$124.47	$124.45	$124.50
Purchase #2	$172.30	12.362%	$193.5997	$193.60	$193.60	$193.60
Purchase #3	$219.69	11.455%	$244.8555	$244.86	$244.85	$244.90
Purchase #4	$19.51	13.562%	$22.1559	$22.16	$22.15	$22.20
Purchase #5	$144.56	6.435%	$153.8624	$153.86	$153.85	$153.90
Purchase #6	$57.53	3.140%	$59.3364	$59.34	$59.35	$59.30
Purchase #7	$221.74	7.527%	$238.4304	$238.43	$238.45	$238.40
7 purchase totals =	$950.28		$1,036.7116	$1,036.72	$1,036.70	$1,036.80