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	$65.50	7.739%	$70.569	$70.57	$70.55	$70.60
Purchase #2	$69.25	12.308%	$77.7733	$77.77	$77.75	$77.80
Purchase #3	$43.29	12.422%	$48.6675	$48.67	$48.65	$48.70
Purchase #4	$34.39	5.102%	$36.1446	$36.14	$36.15	$36.10
Purchase #5	$145.80	8.753%	$158.5619	$158.56	$158.55	$158.60
Purchase #6	$247.27	11.574%	$275.889	$275.89	$275.90	$275.90
Purchase #7	$148.77	4.338%	$155.2236	$155.22	$155.20	$155.20
7 purchase totals =	$754.27		$822.8289	$822.82	$822.75	$822.90