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	$200.82	8.418%	$217.725	$217.73	$217.75	$217.70
Purchase #2	$43.57	11.806%	$48.7139	$48.71	$48.70	$48.70
Purchase #3	$12.29	6.337%	$13.0688	$13.07	$13.05	$13.10
Purchase #4	$190.66	11.642%	$212.8566	$212.86	$212.85	$212.90
Purchase #5	$131.80	10.746%	$145.9632	$145.96	$145.95	$146.00
Purchase #6	$100.30	11.186%	$111.5196	$111.52	$111.50	$111.50
Purchase #7	$111.38	9.197%	$121.6236	$121.62	$121.60	$121.60
7 purchase totals =	$790.82		$871.4707	$871.47	$871.40	$871.50