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	$81.79	4.724%	$85.6538	$85.65	$85.65	$85.70
Purchase #2	$242.70	5.152%	$255.2039	$255.20	$255.20	$255.20
Purchase #3	$97.41	11.557%	$108.6677	$108.67	$108.65	$108.70
Purchase #4	$105.93	7.561%	$113.9394	$113.94	$113.95	$113.90
Purchase #5	$45.45	6.514%	$48.4106	$48.41	$48.40	$48.40
Purchase #6	$63.60	6.473%	$67.7168	$67.72	$67.70	$67.70
Purchase #7	$156.46	10.194%	$172.4095	$172.41	$172.40	$172.40
7 purchase totals =	$793.34		$852.0017	$852.00	$851.95	$852.00