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	$172.63	12.762%	$194.661	$194.66	$194.65	$194.70
Purchase #2	$233.30	9.785%	$256.1284	$256.13	$256.15	$256.10
Purchase #3	$45.78	7.457%	$49.1938	$49.19	$49.20	$49.20
Purchase #4	$144.73	13.733%	$164.6058	$164.61	$164.60	$164.60
Purchase #5	$177.94	7.406%	$191.1182	$191.12	$191.10	$191.10
Purchase #6	$120.46	8.403%	$130.5823	$130.58	$130.60	$130.60
Purchase #7	$38.87	9.441%	$42.5397	$42.54	$42.55	$42.50
7 purchase totals =	$933.71		$1,028.8292	$1,028.83	$1,028.85	$1,028.80