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	$168.80	12.858%	$190.5043	$190.50	$190.50	$190.50
Purchase #2	$14.53	10.392%	$16.04	$16.04	$16.05	$16.00
Purchase #3	$143.82	5.803%	$152.1659	$152.17	$152.15	$152.20
Purchase #4	$170.63	7.468%	$183.3726	$183.37	$183.35	$183.40
Purchase #5	$247.70	12.406%	$278.4297	$278.43	$278.45	$278.40
Purchase #6	$50.51	8.661%	$54.8847	$54.88	$54.90	$54.90
Purchase #7	$196.67	7.196%	$210.8224	$210.82	$210.80	$210.80
7 purchase totals =	$992.66		$1,086.2196	$1,086.21	$1,086.20	$1,086.20