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	$169.50	3.390%	$175.2461	$175.25	$175.25	$175.20
Purchase #2	$213.31	4.260%	$222.397	$222.40	$222.40	$222.40
Purchase #3	$144.60	9.688%	$158.6088	$158.61	$158.60	$158.60
Purchase #4	$90.63	10.837%	$100.4516	$100.45	$100.45	$100.50
Purchase #5	$43.51	11.377%	$48.4601	$48.46	$48.45	$48.50
Purchase #6	$132.33	6.686%	$141.1776	$141.18	$141.20	$141.20
Purchase #7	$80.35	6.764%	$85.7849	$85.78	$85.80	$85.80
7 purchase totals =	$874.23		$932.1261	$932.13	$932.15	$932.20