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	$234.76	8.691%	$255.163	$255.16	$255.15	$255.20
Purchase #2	$178.42	10.325%	$196.8419	$196.84	$196.85	$196.80
Purchase #3	$145.84	6.633%	$155.5136	$155.51	$155.50	$155.50
Purchase #4	$79.67	9.554%	$87.2817	$87.28	$87.30	$87.30
Purchase #5	$154.95	11.286%	$172.4377	$172.44	$172.45	$172.40
Purchase #6	$164.40	7.351%	$176.485	$176.49	$176.50	$176.50
Purchase #7	$200.51	4.469%	$209.4708	$209.47	$209.45	$209.50
7 purchase totals =	$1,158.55		$1,253.1937	$1,253.19	$1,253.20	$1,253.20