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	$92.59	13.609%	$105.1906	$105.19	$105.20	$105.20
Purchase #2	$130.82	5.277%	$137.7234	$137.72	$137.70	$137.70
Purchase #3	$94.25	11.358%	$104.9549	$104.95	$104.95	$105.00
Purchase #4	$223.51	3.427%	$231.1697	$231.17	$231.15	$231.20
Purchase #5	$78.82	4.230%	$82.1541	$82.15	$82.15	$82.20
Purchase #6	$235.48	10.733%	$260.7541	$260.75	$260.75	$260.80
Purchase #7	$113.71	10.680%	$125.8542	$125.85	$125.85	$125.90
7 purchase totals =	$969.18		$1,047.8010	$1,047.78	$1,047.75	$1,048.00