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	$208.50	6.615%	$222.2923	$222.29	$222.30	$222.30
Purchase #2	$38.51	13.336%	$43.6457	$43.65	$43.65	$43.60
Purchase #3	$34.37	13.627%	$39.0536	$39.05	$39.05	$39.10
Purchase #4	$150.42	5.573%	$158.8029	$158.80	$158.80	$158.80
Purchase #5	$95.78	4.823%	$100.3995	$100.40	$100.40	$100.40
Purchase #6	$134.34	7.719%	$144.7097	$144.71	$144.70	$144.70
Purchase #7	$140.79	11.823%	$157.4356	$157.44	$157.45	$157.40
7 purchase totals =	$802.71		$866.3393	$866.34	$866.35	$866.30