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	$152.98	8.851%	$166.5203	$166.52	$166.50	$166.50
Purchase #2	$146.79	8.353%	$159.0514	$159.05	$159.05	$159.10
Purchase #3	$222.81	11.444%	$248.3084	$248.31	$248.30	$248.30
Purchase #4	$125.42	4.663%	$131.2683	$131.27	$131.25	$131.30
Purchase #5	$157.76	12.128%	$176.8931	$176.89	$176.90	$176.90
Purchase #6	$32.93	13.166%	$37.2656	$37.27	$37.25	$37.30
Purchase #7	$234.65	7.850%	$253.07	$253.07	$253.05	$253.10
7 purchase totals =	$1,073.34		$1,172.3771	$1,172.38	$1,172.30	$1,172.50