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	$173.32	13.714%	$197.0891	$197.09	$197.10	$197.10
Purchase #2	$208.55	9.870%	$229.1339	$229.13	$229.15	$229.10
Purchase #3	$104.88	6.682%	$111.8881	$111.89	$111.90	$111.90
Purchase #4	$33.43	5.445%	$35.2503	$35.25	$35.25	$35.30
Purchase #5	$165.47	10.173%	$182.3033	$182.30	$182.30	$182.30
Purchase #6	$61.38	9.203%	$67.0288	$67.03	$67.05	$67.00
Purchase #7	$89.59	4.795%	$93.8858	$93.89	$93.90	$93.90
7 purchase totals =	$836.62		$916.5793	$916.58	$916.65	$916.60