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	$203.70	11.652%	$227.4351	$227.44	$227.45	$227.40
Purchase #2	$203.26	13.160%	$230.009	$230.01	$230.00	$230.00
Purchase #3	$45.28	10.287%	$49.938	$49.94	$49.95	$49.90
Purchase #4	$189.95	11.666%	$212.1096	$212.11	$212.10	$212.10
Purchase #5	$184.78	12.756%	$208.3505	$208.35	$208.35	$208.40
Purchase #6	$87.95	13.484%	$99.8092	$99.81	$99.80	$99.80
Purchase #7	$167.53	3.224%	$172.9312	$172.93	$172.95	$172.90
7 purchase totals =	$1,082.45		$1,200.5826	$1,200.59	$1,200.60	$1,200.50