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	$101.36	10.143%	$111.6409	$111.64	$111.65	$111.60
Purchase #2	$143.56	8.599%	$155.9047	$155.90	$155.90	$155.90
Purchase #3	$235.72	7.707%	$253.8869	$253.89	$253.90	$253.90
Purchase #4	$65.78	7.629%	$70.7984	$70.80	$70.80	$70.80
Purchase #5	$239.64	6.806%	$255.9499	$255.95	$255.95	$255.90
Purchase #6	$16.80	8.410%	$18.2129	$18.21	$18.20	$18.20
Purchase #7	$43.72	11.394%	$48.7015	$48.70	$48.70	$48.70
7 purchase totals =	$846.58		$915.0952	$915.09	$915.10	$915.00