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	$66.69	8.821%	$72.5727	$72.57	$72.55	$72.60
Purchase #2	$50.59	4.396%	$52.8139	$52.81	$52.80	$52.80
Purchase #3	$239.29	5.720%	$252.9774	$252.98	$253.00	$253.00
Purchase #4	$74.34	5.569%	$78.48	$78.48	$78.50	$78.50
Purchase #5	$31.32	9.507%	$34.2976	$34.30	$34.30	$34.30
Purchase #6	$216.96	7.501%	$233.2342	$233.23	$233.25	$233.20
Purchase #7	$69.52	9.552%	$76.1606	$76.16	$76.15	$76.20
7 purchase totals =	$748.71		$800.5364	$800.53	$800.55	$800.60