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	$92.55	6.466%	$98.5343	$98.53	$98.55	$98.50
Purchase #2	$142.45	7.576%	$153.242	$153.24	$153.25	$153.20
Purchase #3	$61.27	5.263%	$64.4946	$64.49	$64.50	$64.50
Purchase #4	$143.52	11.780%	$160.4267	$160.43	$160.45	$160.40
Purchase #5	$123.77	7.229%	$132.7173	$132.72	$132.70	$132.70
Purchase #6	$160.55	7.290%	$172.2541	$172.25	$172.25	$172.30
Purchase #7	$157.45	7.434%	$169.1548	$169.15	$169.15	$169.20
7 purchase totals =	$881.56		$950.8238	$950.81	$950.85	$950.80