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	$92.60	12.428%	$104.1083	$104.11	$104.10	$104.10
Purchase #2	$74.39	12.833%	$83.9365	$83.94	$83.95	$83.90
Purchase #3	$11.90	6.698%	$12.6971	$12.70	$12.70	$12.70
Purchase #4	$197.89	6.586%	$210.923	$210.92	$210.90	$210.90
Purchase #5	$10.92	6.277%	$11.6054	$11.61	$11.60	$11.60
Purchase #6	$165.66	8.229%	$179.2922	$179.29	$179.30	$179.30
Purchase #7	$78.89	5.460%	$83.1974	$83.20	$83.20	$83.20
7 purchase totals =	$632.25		$685.7599	$685.77	$685.75	$685.70