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	$54.87	11.568%	$61.2174	$61.22	$61.20	$61.20
Purchase #2	$147.66	5.364%	$155.5805	$155.58	$155.60	$155.60
Purchase #3	$195.42	5.236%	$205.6522	$205.65	$205.65	$205.70
Purchase #4	$29.69	12.408%	$33.3739	$33.37	$33.35	$33.40
Purchase #5	$151.91	13.534%	$172.4695	$172.47	$172.45	$172.50
Purchase #6	$58.40	8.699%	$63.4802	$63.48	$63.50	$63.50
Purchase #7	$10.87	13.323%	$12.3182	$12.32	$12.30	$12.30
7 purchase totals =	$648.82		$704.0919	$704.09	$704.05	$704.20