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	$21.75	4.196%	$22.6626	$22.66	$22.65	$22.70
Purchase #2	$40.35	12.371%	$45.3417	$45.34	$45.35	$45.30
Purchase #3	$113.72	11.714%	$127.0412	$127.04	$127.05	$127.00
Purchase #4	$33.42	11.537%	$37.2757	$37.28	$37.30	$37.30
Purchase #5	$16.92	3.138%	$17.4509	$17.45	$17.45	$17.50
Purchase #6	$232.82	11.463%	$259.5082	$259.51	$259.50	$259.50
Purchase #7	$34.56	13.617%	$39.266	$39.27	$39.25	$39.30
7 purchase totals =	$493.54		$548.5463	$548.55	$548.55	$548.60