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	$136.60	8.261%	$147.8845	$147.88	$147.90	$147.90
Purchase #2	$40.94	8.624%	$44.4707	$44.47	$44.45	$44.50
Purchase #3	$138.80	12.221%	$155.7627	$155.76	$155.75	$155.80
Purchase #4	$144.49	5.486%	$152.4167	$152.42	$152.40	$152.40
Purchase #5	$213.28	4.619%	$223.1314	$223.13	$223.15	$223.10
Purchase #6	$146.41	4.232%	$152.6061	$152.61	$152.60	$152.60
Purchase #7	$148.68	11.313%	$165.5002	$165.50	$165.50	$165.50
7 purchase totals =	$969.20		$1,041.7723	$1,041.77	$1,041.75	$1,041.80