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	$160.54	8.570%	$174.2983	$174.30	$174.30	$174.30
Purchase #2	$222.51	11.301%	$247.6559	$247.66	$247.65	$247.70
Purchase #3	$105.55	5.659%	$111.5231	$111.52	$111.50	$111.50
Purchase #4	$18.90	10.594%	$20.9023	$20.90	$20.90	$20.90
Purchase #5	$59.82	12.371%	$67.2203	$67.22	$67.20	$67.20
Purchase #6	$189.36	12.122%	$212.3142	$212.31	$212.30	$212.30
Purchase #7	$47.74	6.379%	$50.7853	$50.79	$50.80	$50.80
7 purchase totals =	$804.42		$884.6994	$884.70	$884.65	$884.70