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	$242.37	13.530%	$275.1627	$275.16	$275.15	$275.20
Purchase #2	$100.83	7.117%	$108.0061	$108.01	$108.00	$108.00
Purchase #3	$164.98	8.447%	$178.9159	$178.92	$178.90	$178.90
Purchase #4	$217.59	5.453%	$229.4552	$229.46	$229.45	$229.50
Purchase #5	$203.76	8.848%	$221.7887	$221.79	$221.80	$221.80
Purchase #6	$78.80	8.580%	$85.561	$85.56	$85.55	$85.60
Purchase #7	$229.57	10.478%	$253.6243	$253.62	$253.60	$253.60
7 purchase totals =	$1,237.90		$1,352.5139	$1,352.52	$1,352.45	$1,352.60