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	$48.60	8.493%	$52.7276	$52.73	$52.75	$52.70
Purchase #2	$155.39	7.459%	$166.9805	$166.98	$167.00	$167.00
Purchase #3	$139.33	9.717%	$152.8687	$152.87	$152.85	$152.90
Purchase #4	$121.52	8.294%	$131.5989	$131.60	$131.60	$131.60
Purchase #5	$124.94	13.733%	$142.098	$142.10	$142.10	$142.10
Purchase #6	$199.61	10.737%	$221.0421	$221.04	$221.05	$221.00
Purchase #7	$74.43	12.186%	$83.5	$83.50	$83.50	$83.50
7 purchase totals =	$863.82		$950.8158	$950.82	$950.85	$950.80