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	$221.81	7.526%	$238.5034	$238.50	$238.50	$238.50
Purchase #2	$128.37	3.473%	$132.8283	$132.83	$132.85	$132.80
Purchase #3	$107.60	3.527%	$111.3951	$111.40	$111.40	$111.40
Purchase #4	$239.79	4.858%	$251.439	$251.44	$251.45	$251.40
Purchase #5	$134.83	13.242%	$152.6842	$152.68	$152.70	$152.70
Purchase #6	$9.47	7.461%	$10.1766	$10.18	$10.20	$10.20
Purchase #7	$235.35	8.597%	$255.583	$255.58	$255.60	$255.60
7 purchase totals =	$1,077.22		$1,152.6096	$1,152.61	$1,152.70	$1,152.60