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	$228.73	11.410%	$254.8281	$254.83	$254.85	$254.80
Purchase #2	$78.43	13.302%	$88.8628	$88.86	$88.85	$88.90
Purchase #3	$106.41	10.839%	$117.9438	$117.94	$117.95	$117.90
Purchase #4	$76.92	13.279%	$87.1342	$87.13	$87.15	$87.10
Purchase #5	$111.66	11.469%	$124.4663	$124.47	$124.45	$124.50
Purchase #6	$43.94	9.766%	$48.2312	$48.23	$48.25	$48.20
Purchase #7	$164.85	5.313%	$173.6085	$173.61	$173.60	$173.60
7 purchase totals =	$810.94		$895.0749	$895.07	$895.10	$895.00