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	$215.67	8.574%	$234.1615	$234.16	$234.15	$234.20
Purchase #2	$37.51	6.680%	$40.0157	$40.02	$40.00	$40.00
Purchase #3	$48.62	8.370%	$52.6895	$52.69	$52.70	$52.70
Purchase #4	$88.88	13.575%	$100.9455	$100.95	$100.95	$100.90
Purchase #5	$164.90	4.726%	$172.6932	$172.69	$172.70	$172.70
Purchase #6	$38.61	5.410%	$40.6988	$40.70	$40.70	$40.70
Purchase #7	$40.43	13.324%	$45.8169	$45.82	$45.80	$45.80
7 purchase totals =	$634.62		$687.0211	$687.03	$687.00	$687.00