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	$152.29	4.613%	$159.3151	$159.32	$159.30	$159.30
Purchase #2	$45.89	5.593%	$48.4566	$48.46	$48.45	$48.50
Purchase #3	$172.56	11.203%	$191.8919	$191.89	$191.90	$191.90
Purchase #4	$135.53	5.476%	$142.9516	$142.95	$142.95	$143.00
Purchase #5	$51.99	9.383%	$56.8682	$56.87	$56.85	$56.90
Purchase #6	$204.58	6.123%	$217.1064	$217.11	$217.10	$217.10
Purchase #7	$44.83	12.594%	$50.4759	$50.48	$50.50	$50.50
7 purchase totals =	$807.67		$867.0657	$867.08	$867.05	$867.20