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	$42.25	8.298%	$45.7559	$45.76	$45.75	$45.80
Purchase #2	$142.52	8.762%	$155.0076	$155.01	$155.00	$155.00
Purchase #3	$22.32	4.345%	$23.2898	$23.29	$23.30	$23.30
Purchase #4	$53.72	10.401%	$59.3074	$59.31	$59.30	$59.30
Purchase #5	$140.51	9.485%	$153.8374	$153.84	$153.85	$153.80
Purchase #6	$170.31	6.824%	$181.932	$181.93	$181.95	$181.90
Purchase #7	$111.96	12.790%	$126.2797	$126.28	$126.30	$126.30
7 purchase totals =	$683.59		$745.4098	$745.42	$745.45	$745.40