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	$200.30	12.161%	$224.6585	$224.66	$224.65	$224.70
Purchase #2	$93.31	7.578%	$100.381	$100.38	$100.40	$100.40
Purchase #3	$64.71	9.464%	$70.8342	$70.83	$70.85	$70.80
Purchase #4	$28.80	11.655%	$32.1566	$32.16	$32.15	$32.20
Purchase #5	$131.78	8.486%	$142.9629	$142.96	$142.95	$143.00
Purchase #6	$234.29	9.339%	$256.1703	$256.17	$256.15	$256.20
Purchase #7	$126.56	6.533%	$134.8282	$134.83	$134.85	$134.80
7 purchase totals =	$879.75		$961.9917	$961.99	$962.00	$962.10