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	$196.83	9.588%	$215.7021	$215.70	$215.70	$215.70
Purchase #2	$203.75	8.609%	$221.2908	$221.29	$221.30	$221.30
Purchase #3	$191.28	4.634%	$200.1439	$200.14	$200.15	$200.10
Purchase #4	$48.41	11.118%	$53.7922	$53.79	$53.80	$53.80
Purchase #5	$143.81	9.594%	$157.6071	$157.61	$157.60	$157.60
Purchase #6	$214.35	12.410%	$240.9508	$240.95	$240.95	$241.00
Purchase #7	$19.32	5.297%	$20.3434	$20.34	$20.35	$20.30
7 purchase totals =	$1,017.75		$1,109.8303	$1,109.82	$1,109.85	$1,109.80