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	$143.77	11.221%	$159.9024	$159.90	$159.90	$159.90
Purchase #2	$11.58	8.707%	$12.5883	$12.59	$12.60	$12.60
Purchase #3	$139.45	11.163%	$155.0168	$155.02	$155.00	$155.00
Purchase #4	$143.52	7.716%	$154.594	$154.59	$154.60	$154.60
Purchase #5	$240.73	10.566%	$266.1655	$266.17	$266.15	$266.20
Purchase #6	$242.98	5.723%	$256.8857	$256.89	$256.90	$256.90
Purchase #7	$216.59	11.128%	$240.6921	$240.69	$240.70	$240.70
7 purchase totals =	$1,138.62		$1,245.8448	$1,245.85	$1,245.85	$1,245.90