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	$155.84	10.484%	$172.1783	$172.18	$172.20	$172.20
Purchase #2	$48.85	8.191%	$52.8513	$52.85	$52.85	$52.90
Purchase #3	$18.89	13.763%	$21.4898	$21.49	$21.50	$21.50
Purchase #4	$224.85	5.621%	$237.4888	$237.49	$237.50	$237.50
Purchase #5	$189.30	10.793%	$209.7311	$209.73	$209.75	$209.70
Purchase #6	$96.47	12.629%	$108.6532	$108.65	$108.65	$108.70
Purchase #7	$209.45	3.168%	$216.0854	$216.09	$216.10	$216.10
7 purchase totals =	$943.65		$1,018.4779	$1,018.48	$1,018.55	$1,018.60