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	$69.43	5.680%	$73.3736	$73.37	$73.35	$73.40
Purchase #2	$238.60	11.105%	$265.0965	$265.10	$265.10	$265.10
Purchase #3	$141.91	3.563%	$146.9663	$146.97	$146.95	$147.00
Purchase #4	$214.70	3.833%	$222.9295	$222.93	$222.95	$222.90
Purchase #5	$175.85	13.805%	$200.1261	$200.13	$200.15	$200.10
Purchase #6	$227.69	13.187%	$257.7155	$257.72	$257.70	$257.70
Purchase #7	$217.31	12.429%	$244.3195	$244.32	$244.30	$244.30
7 purchase totals =	$1,285.49		$1,410.5270	$1,410.54	$1,410.50	$1,410.50