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	$144.88	3.806%	$150.3941	$150.39	$150.40	$150.40
Purchase #2	$125.73	4.312%	$131.1515	$131.15	$131.15	$131.20
Purchase #3	$247.54	5.749%	$261.7711	$261.77	$261.75	$261.80
Purchase #4	$143.45	8.196%	$155.2072	$155.21	$155.20	$155.20
Purchase #5	$163.70	5.378%	$172.5038	$172.50	$172.50	$172.50
Purchase #6	$85.29	9.383%	$93.2928	$93.29	$93.30	$93.30
Purchase #7	$93.35	6.300%	$99.2311	$99.23	$99.25	$99.20
7 purchase totals =	$1,003.94		$1,063.5516	$1,063.54	$1,063.55	$1,063.60