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	$204.82	4.648%	$214.34	$214.34	$214.35	$214.30
Purchase #2	$18.94	10.153%	$20.863	$20.86	$20.85	$20.90
Purchase #3	$135.68	11.578%	$151.389	$151.39	$151.40	$151.40
Purchase #4	$205.31	11.388%	$228.6907	$228.69	$228.70	$228.70
Purchase #5	$97.93	7.406%	$105.1827	$105.18	$105.20	$105.20
Purchase #6	$80.46	12.615%	$90.61	$90.61	$90.60	$90.60
Purchase #7	$100.27	4.853%	$105.1361	$105.14	$105.15	$105.10
7 purchase totals =	$843.41		$916.2115	$916.21	$916.25	$916.20