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	$12.77	13.484%	$14.4919	$14.49	$14.50	$14.50
Purchase #2	$247.46	11.540%	$276.0169	$276.02	$276.00	$276.00
Purchase #3	$97.42	8.308%	$105.5137	$105.51	$105.50	$105.50
Purchase #4	$41.39	5.294%	$43.5812	$43.58	$43.60	$43.60
Purchase #5	$57.89	13.750%	$65.8499	$65.85	$65.85	$65.80
Purchase #6	$216.99	13.504%	$246.2923	$246.29	$246.30	$246.30
Purchase #7	$169.34	12.272%	$190.1214	$190.12	$190.10	$190.10
7 purchase totals =	$843.26		$941.8673	$941.86	$941.85	$941.80