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	$140.31	11.775%	$156.8315	$156.83	$156.85	$156.80
Purchase #2	$94.94	13.247%	$107.5167	$107.52	$107.50	$107.50
Purchase #3	$192.44	6.592%	$205.1256	$205.13	$205.15	$205.10
Purchase #4	$155.84	10.622%	$172.3933	$172.39	$172.40	$172.40
Purchase #5	$140.61	7.342%	$150.9336	$150.93	$150.95	$150.90
Purchase #6	$11.61	11.417%	$12.9355	$12.94	$12.95	$12.90
Purchase #7	$192.29	11.513%	$214.4283	$214.43	$214.45	$214.40
7 purchase totals =	$928.04		$1,020.1645	$1,020.17	$1,020.25	$1,020.00