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	$32.78	13.594%	$37.2361	$37.24	$37.25	$37.20
Purchase #2	$112.68	6.500%	$120.0042	$120.00	$120.00	$120.00
Purchase #3	$85.92	13.162%	$97.2288	$97.23	$97.25	$97.20
Purchase #4	$173.38	10.831%	$192.1588	$192.16	$192.15	$192.20
Purchase #5	$170.88	11.103%	$189.8528	$189.85	$189.85	$189.90
Purchase #6	$203.30	9.491%	$222.5952	$222.60	$222.60	$222.60
Purchase #7	$236.91	9.689%	$259.8642	$259.86	$259.85	$259.90
7 purchase totals =	$1,015.85		$1,118.9401	$1,118.94	$1,118.95	$1,119.00