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	$134.31	5.109%	$141.1719	$141.17	$141.15	$141.20
Purchase #2	$185.82	12.165%	$208.425	$208.43	$208.45	$208.40
Purchase #3	$132.47	5.209%	$139.3704	$139.37	$139.35	$139.40
Purchase #4	$64.27	10.610%	$71.089	$71.09	$71.10	$71.10
Purchase #5	$44.69	8.500%	$48.4887	$48.49	$48.50	$48.50
Purchase #6	$220.72	11.676%	$246.4913	$246.49	$246.50	$246.50
Purchase #7	$58.53	3.812%	$60.7612	$60.76	$60.75	$60.80
7 purchase totals =	$840.81		$915.7975	$915.80	$915.80	$915.90