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	$153.67	12.204%	$172.4239	$172.42	$172.40	$172.40
Purchase #2	$90.31	4.311%	$94.2033	$94.20	$94.20	$94.20
Purchase #3	$161.55	7.461%	$173.6032	$173.60	$173.60	$173.60
Purchase #4	$61.54	7.455%	$66.1278	$66.13	$66.15	$66.10
Purchase #5	$169.71	3.594%	$175.8094	$175.81	$175.80	$175.80
Purchase #6	$94.58	4.462%	$98.8002	$98.80	$98.80	$98.80
Purchase #7	$41.57	8.504%	$45.1051	$45.11	$45.10	$45.10
7 purchase totals =	$772.93		$826.0729	$826.07	$826.05	$826.00