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	$105.43	5.530%	$111.2603	$111.26	$111.25	$111.30
Purchase #2	$11.65	10.862%	$12.9154	$12.92	$12.90	$12.90
Purchase #3	$55.78	11.860%	$62.3955	$62.40	$62.40	$62.40
Purchase #4	$54.39	13.267%	$61.6059	$61.61	$61.60	$61.60
Purchase #5	$160.94	7.277%	$172.6516	$172.65	$172.65	$172.70
Purchase #6	$39.45	12.548%	$44.4002	$44.40	$44.40	$44.40
Purchase #7	$85.91	7.752%	$92.5697	$92.57	$92.55	$92.60
7 purchase totals =	$513.55		$557.7986	$557.81	$557.75	$557.90