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	$215.51	3.336%	$222.6994	$222.70	$222.70	$222.70
Purchase #2	$117.59	5.257%	$123.7717	$123.77	$123.75	$123.80
Purchase #3	$13.80	13.720%	$15.6934	$15.69	$15.70	$15.70
Purchase #4	$32.27	13.529%	$36.6358	$36.64	$36.65	$36.60
Purchase #5	$153.60	12.117%	$172.2117	$172.21	$172.20	$172.20
Purchase #6	$108.91	10.716%	$120.5808	$120.58	$120.60	$120.60
Purchase #7	$112.50	3.386%	$116.3093	$116.31	$116.30	$116.30
7 purchase totals =	$754.18		$807.9021	$807.90	$807.90	$807.90