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	$60.34	10.363%	$66.593	$66.59	$66.60	$66.60
Purchase #2	$59.33	5.576%	$62.6382	$62.64	$62.65	$62.60
Purchase #3	$48.72	5.250%	$51.2778	$51.28	$51.30	$51.30
Purchase #4	$153.83	3.874%	$159.7894	$159.79	$159.80	$159.80
Purchase #5	$67.45	5.124%	$70.9061	$70.91	$70.90	$70.90
Purchase #6	$111.90	5.741%	$118.3242	$118.32	$118.30	$118.30
Purchase #7	$209.86	6.821%	$224.1746	$224.17	$224.15	$224.20
7 purchase totals =	$711.43		$753.7033	$753.70	$753.70	$753.70