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	$248.32	8.286%	$268.8958	$268.90	$268.90	$268.90
Purchase #2	$107.57	8.286%	$116.4833	$116.48	$116.50	$116.50
Purchase #3	$204.97	10.829%	$227.1662	$227.17	$227.15	$227.20
Purchase #4	$226.60	13.184%	$256.4749	$256.47	$256.45	$256.50
Purchase #5	$135.74	8.222%	$146.9005	$146.90	$146.90	$146.90
Purchase #6	$138.89	13.346%	$157.4263	$157.43	$157.45	$157.40
Purchase #7	$78.62	5.378%	$82.8482	$82.85	$82.85	$82.80
7 purchase totals =	$1,140.71		$1,256.1952	$1,256.20	$1,256.20	$1,256.20