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	$154.30	13.682%	$175.4113	$175.41	$175.40	$175.40
Purchase #2	$47.76	10.796%	$52.9162	$52.92	$52.90	$52.90
Purchase #3	$124.95	4.733%	$130.8639	$130.86	$130.85	$130.90
Purchase #4	$196.66	9.387%	$215.1205	$215.12	$215.10	$215.10
Purchase #5	$247.90	5.873%	$262.4592	$262.46	$262.45	$262.50
Purchase #6	$230.53	11.145%	$256.2226	$256.22	$256.20	$256.20
Purchase #7	$214.28	13.385%	$242.9614	$242.96	$242.95	$243.00
7 purchase totals =	$1,216.38		$1,335.9551	$1,335.95	$1,335.85	$1,336.00