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	$102.82	8.603%	$111.6656	$111.67	$111.65	$111.70
Purchase #2	$75.30	7.390%	$80.8647	$80.86	$80.85	$80.90
Purchase #3	$70.41	5.753%	$74.4607	$74.46	$74.45	$74.50
Purchase #4	$118.35	10.222%	$130.4477	$130.45	$130.45	$130.40
Purchase #5	$95.83	5.600%	$101.1965	$101.20	$101.20	$101.20
Purchase #6	$13.94	3.569%	$14.4375	$14.44	$14.45	$14.40
Purchase #7	$48.75	3.518%	$50.465	$50.47	$50.45	$50.50
7 purchase totals =	$525.40		$563.5377	$563.55	$563.50	$563.60