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	$67.89	13.197%	$76.8494	$76.85	$76.85	$76.80
Purchase #2	$182.41	7.707%	$196.4683	$196.47	$196.45	$196.50
Purchase #3	$247.89	5.288%	$260.9984	$261.00	$261.00	$261.00
Purchase #4	$101.76	9.105%	$111.0252	$111.03	$111.05	$111.00
Purchase #5	$141.85	11.492%	$158.1514	$158.15	$158.15	$158.20
Purchase #6	$94.94	3.800%	$98.5477	$98.55	$98.55	$98.50
Purchase #7	$48.93	10.529%	$54.0818	$54.08	$54.10	$54.10
7 purchase totals =	$885.67		$956.1222	$956.13	$956.15	$956.10