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	$195.41	13.153%	$221.1123	$221.11	$221.10	$221.10
Purchase #2	$179.47	11.553%	$200.2042	$200.20	$200.20	$200.20
Purchase #3	$175.71	7.526%	$188.9339	$188.93	$188.95	$188.90
Purchase #4	$48.89	7.357%	$52.4868	$52.49	$52.50	$52.50
Purchase #5	$16.51	12.204%	$18.5249	$18.52	$18.50	$18.50
Purchase #6	$140.41	5.468%	$148.0876	$148.09	$148.10	$148.10
Purchase #7	$31.33	7.126%	$33.5626	$33.56	$33.55	$33.60
7 purchase totals =	$787.73		$862.9123	$862.90	$862.90	$862.90