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	$28.74	12.388%	$32.3003	$32.30	$32.30	$32.30
Purchase #2	$39.78	8.562%	$43.186	$43.19	$43.20	$43.20
Purchase #3	$78.36	7.565%	$84.2879	$84.29	$84.30	$84.30
Purchase #4	$19.42	5.274%	$20.4442	$20.44	$20.45	$20.40
Purchase #5	$58.61	5.635%	$61.9127	$61.91	$61.90	$61.90
Purchase #6	$51.61	7.625%	$55.5453	$55.55	$55.55	$55.50
Purchase #7	$160.51	3.200%	$165.6463	$165.65	$165.65	$165.60
7 purchase totals =	$437.03		$463.3227	$463.33	$463.35	$463.20