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	$158.68	4.339%	$165.5651	$165.57	$165.55	$165.60
Purchase #2	$132.37	10.550%	$146.335	$146.34	$146.35	$146.30
Purchase #3	$106.95	11.118%	$118.8407	$118.84	$118.85	$118.80
Purchase #4	$103.33	4.709%	$108.1958	$108.20	$108.20	$108.20
Purchase #5	$10.60	5.160%	$11.147	$11.15	$11.15	$11.10
Purchase #6	$111.82	12.824%	$126.1598	$126.16	$126.15	$126.20
Purchase #7	$78.76	8.118%	$85.1537	$85.15	$85.15	$85.20
7 purchase totals =	$702.51		$761.3971	$761.41	$761.40	$761.40