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	$101.85	9.544%	$111.5706	$111.57	$111.55	$111.60
Purchase #2	$9.61	8.568%	$10.4334	$10.43	$10.45	$10.40
Purchase #3	$112.92	10.572%	$124.8579	$124.86	$124.85	$124.90
Purchase #4	$6.45	6.150%	$6.8467	$6.85	$6.85	$6.80
Purchase #5	$121.79	5.382%	$128.3447	$128.34	$128.35	$128.30
Purchase #6	$47.46	8.619%	$51.5506	$51.55	$51.55	$51.60
Purchase #7	$72.80	5.184%	$76.574	$76.57	$76.55	$76.60
7 purchase totals =	$472.88		$510.1779	$510.17	$510.15	$510.20