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	$201.53	7.108%	$215.8548	$215.85	$215.85	$215.90
Purchase #2	$122.95	11.602%	$137.2147	$137.21	$137.20	$137.20
Purchase #3	$223.51	7.768%	$240.8723	$240.87	$240.85	$240.90
Purchase #4	$56.77	4.588%	$59.3746	$59.37	$59.35	$59.40
Purchase #5	$185.99	12.344%	$208.9486	$208.95	$208.95	$208.90
Purchase #6	$95.33	8.181%	$103.1289	$103.13	$103.15	$103.10
Purchase #7	$111.93	10.574%	$123.7655	$123.77	$123.75	$123.80
7 purchase totals =	$998.01		$1,089.1594	$1,089.15	$1,089.10	$1,089.20