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	$233.31	4.175%	$243.0507	$243.05	$243.05	$243.10
Purchase #2	$137.43	4.434%	$143.5236	$143.52	$143.50	$143.50
Purchase #3	$166.90	10.355%	$184.1825	$184.18	$184.20	$184.20
Purchase #4	$154.61	11.342%	$172.1459	$172.15	$172.15	$172.10
Purchase #5	$117.39	3.610%	$121.6278	$121.63	$121.65	$121.60
Purchase #6	$10.78	3.707%	$11.1796	$11.18	$11.20	$11.20
Purchase #7	$141.51	10.140%	$155.8591	$155.86	$155.85	$155.90
7 purchase totals =	$961.93		$1,031.5692	$1,031.57	$1,031.60	$1,031.60