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	$125.89	11.110%	$139.8764	$139.88	$139.90	$139.90
Purchase #2	$52.27	5.125%	$54.9488	$54.95	$54.95	$54.90
Purchase #3	$56.40	5.514%	$59.5099	$59.51	$59.50	$59.50
Purchase #4	$220.88	5.716%	$233.5055	$233.51	$233.50	$233.50
Purchase #5	$213.45	3.758%	$221.4715	$221.47	$221.45	$221.50
Purchase #6	$57.89	6.248%	$61.507	$61.51	$61.50	$61.50
Purchase #7	$161.79	6.533%	$172.3597	$172.36	$172.35	$172.40
7 purchase totals =	$888.57		$943.1788	$943.19	$943.15	$943.20