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	$110.66	8.210%	$119.7452	$119.75	$119.75	$119.70
Purchase #2	$146.38	6.239%	$155.5126	$155.51	$155.50	$155.50
Purchase #3	$57.45	11.849%	$64.2573	$64.26	$64.25	$64.30
Purchase #4	$40.92	10.733%	$45.3119	$45.31	$45.30	$45.30
Purchase #5	$169.48	5.314%	$178.4862	$178.49	$178.50	$178.50
Purchase #6	$87.71	9.639%	$96.1644	$96.16	$96.15	$96.20
Purchase #7	$49.42	13.267%	$55.9766	$55.98	$56.00	$56.00
7 purchase totals =	$662.02		$715.4542	$715.46	$715.45	$715.50