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	$106.95	9.307%	$116.9038	$116.90	$116.90	$116.90
Purchase #2	$155.92	8.717%	$169.5115	$169.51	$169.50	$169.50
Purchase #3	$70.77	9.652%	$77.6007	$77.60	$77.60	$77.60
Purchase #4	$79.50	13.408%	$90.1594	$90.16	$90.15	$90.20
Purchase #5	$188.59	4.733%	$197.516	$197.52	$197.50	$197.50
Purchase #6	$236.46	10.846%	$262.1065	$262.11	$262.10	$262.10
Purchase #7	$28.81	13.135%	$32.5942	$32.59	$32.60	$32.60
7 purchase totals =	$867.00		$946.3921	$946.39	$946.35	$946.40