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	$33.95	6.399%	$36.1225	$36.12	$36.10	$36.10
Purchase #2	$10.76	7.530%	$11.5702	$11.57	$11.55	$11.60
Purchase #3	$131.44	11.614%	$146.7054	$146.71	$146.70	$146.70
Purchase #4	$237.91	10.340%	$262.5099	$262.51	$262.50	$262.50
Purchase #5	$244.29	4.837%	$256.1063	$256.11	$256.10	$256.10
Purchase #6	$63.84	12.769%	$71.9917	$71.99	$72.00	$72.00
Purchase #7	$72.72	6.590%	$77.5122	$77.51	$77.50	$77.50
7 purchase totals =	$794.91		$862.5182	$862.52	$862.45	$862.50