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	$172.78	12.610%	$194.5676	$194.57	$194.55	$194.60
Purchase #2	$240.75	8.208%	$260.5108	$260.51	$260.50	$260.50
Purchase #3	$136.35	7.408%	$146.4508	$146.45	$146.45	$146.50
Purchase #4	$144.48	4.784%	$151.3919	$151.39	$151.40	$151.40
Purchase #5	$158.66	13.707%	$180.4075	$180.41	$180.40	$180.40
Purchase #6	$137.67	11.152%	$153.023	$153.02	$153.00	$153.00
Purchase #7	$134.85	13.115%	$152.5356	$152.54	$152.55	$152.50
7 purchase totals =	$1,125.54		$1,238.8872	$1,238.89	$1,238.85	$1,238.90