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	$34.41	9.589%	$37.7096	$37.71	$37.70	$37.70
Purchase #2	$155.84	10.763%	$172.6131	$172.61	$172.60	$172.60
Purchase #3	$247.41	11.620%	$276.159	$276.16	$276.15	$276.20
Purchase #4	$44.85	8.785%	$48.7901	$48.79	$48.80	$48.80
Purchase #5	$38.62	13.375%	$43.7854	$43.79	$43.80	$43.80
Purchase #6	$174.47	7.790%	$188.0612	$188.06	$188.05	$188.10
Purchase #7	$224.60	11.594%	$250.6401	$250.64	$250.65	$250.60
7 purchase totals =	$920.20		$1,017.7585	$1,017.76	$1,017.75	$1,017.80