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	$236.42	11.387%	$263.3411	$263.34	$263.35	$263.30
Purchase #2	$42.38	6.733%	$45.2334	$45.23	$45.25	$45.20
Purchase #3	$217.51	3.209%	$224.4899	$224.49	$224.50	$224.50
Purchase #4	$162.63	6.461%	$173.1375	$173.14	$173.15	$173.10
Purchase #5	$95.64	5.248%	$100.6592	$100.66	$100.65	$100.70
Purchase #6	$42.74	9.673%	$46.8742	$46.87	$46.85	$46.90
Purchase #7	$185.45	5.433%	$195.5255	$195.53	$195.55	$195.50
7 purchase totals =	$982.77		$1,049.2608	$1,049.26	$1,049.30	$1,049.20