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	$83.31	8.565%	$90.4455	$90.45	$90.45	$90.40
Purchase #2	$81.87	12.584%	$92.1725	$92.17	$92.15	$92.20
Purchase #3	$202.75	10.849%	$224.7463	$224.75	$224.75	$224.70
Purchase #4	$80.59	8.530%	$87.4643	$87.46	$87.45	$87.50
Purchase #5	$144.49	10.693%	$159.9403	$159.94	$159.95	$159.90
Purchase #6	$227.59	7.394%	$244.418	$244.42	$244.40	$244.40
Purchase #7	$43.75	4.819%	$45.8583	$45.86	$45.85	$45.90
7 purchase totals =	$864.35		$945.0452	$945.05	$945.00	$945.00