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	$115.81	3.236%	$119.5576	$119.56	$119.55	$119.60
Purchase #2	$42.69	5.522%	$45.0473	$45.05	$45.05	$45.00
Purchase #3	$246.96	5.469%	$260.4662	$260.47	$260.45	$260.50
Purchase #4	$137.37	8.246%	$148.6975	$148.70	$148.70	$148.70
Purchase #5	$172.83	6.405%	$183.8998	$183.90	$183.90	$183.90
Purchase #6	$126.87	13.848%	$144.439	$144.44	$144.45	$144.40
Purchase #7	$40.29	13.598%	$45.7686	$45.77	$45.75	$45.80
7 purchase totals =	$882.82		$947.8760	$947.89	$947.85	$947.90