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	$206.31	10.733%	$228.4533	$228.45	$228.45	$228.50
Purchase #2	$248.53	12.424%	$279.4074	$279.41	$279.40	$279.40
Purchase #3	$91.48	8.765%	$99.4982	$99.50	$99.50	$99.50
Purchase #4	$144.77	7.672%	$155.8768	$155.88	$155.90	$155.90
Purchase #5	$218.30	7.859%	$235.4562	$235.46	$235.45	$235.50
Purchase #6	$137.39	6.624%	$146.4907	$146.49	$146.50	$146.50
Purchase #7	$190.83	6.491%	$203.2168	$203.22	$203.20	$203.20
7 purchase totals =	$1,237.61		$1,348.3994	$1,348.41	$1,348.40	$1,348.50