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	$234.68	8.148%	$253.8017	$253.80	$253.80	$253.80
Purchase #2	$159.65	12.511%	$179.6238	$179.62	$179.60	$179.60
Purchase #3	$154.29	10.484%	$170.4658	$170.47	$170.45	$170.50
Purchase #4	$65.61	12.501%	$73.8119	$73.81	$73.80	$73.80
Purchase #5	$146.83	12.377%	$165.0031	$165.00	$165.00	$165.00
Purchase #6	$156.58	4.647%	$163.8563	$163.86	$163.85	$163.90
Purchase #7	$50.93	7.333%	$54.6647	$54.66	$54.65	$54.70
7 purchase totals =	$968.57		$1,061.2273	$1,061.22	$1,061.15	$1,061.30