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	$250.91	5.148%	$263.8268	$263.83	$263.85	$263.80
Purchase #2	$47.78	11.717%	$53.3784	$53.38	$53.40	$53.40
Purchase #3	$9.72	11.381%	$10.8262	$10.83	$10.85	$10.80
Purchase #4	$158.94	10.519%	$175.6589	$175.66	$175.65	$175.70
Purchase #5	$68.91	13.293%	$78.0702	$78.07	$78.05	$78.10
Purchase #6	$33.55	10.348%	$37.0218	$37.02	$37.00	$37.00
Purchase #7	$172.35	11.613%	$192.365	$192.37	$192.35	$192.40
7 purchase totals =	$742.16		$811.1473	$811.16	$811.15	$811.20