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	$52.94	7.285%	$56.7967	$56.80	$56.80	$56.80
Purchase #2	$241.26	13.771%	$274.4839	$274.48	$274.50	$274.50
Purchase #3	$43.41	4.553%	$45.3865	$45.39	$45.40	$45.40
Purchase #4	$59.91	11.189%	$66.6133	$66.61	$66.60	$66.60
Purchase #5	$169.52	6.208%	$180.0438	$180.04	$180.05	$180.00
Purchase #6	$171.70	9.863%	$188.6348	$188.63	$188.65	$188.60
Purchase #7	$217.86	13.442%	$247.1447	$247.14	$247.15	$247.10
7 purchase totals =	$956.60		$1,059.1037	$1,059.09	$1,059.15	$1,059.00