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	$98.36	11.522%	$109.693	$109.69	$109.70	$109.70
Purchase #2	$87.42	3.863%	$90.797	$90.80	$90.80	$90.80
Purchase #3	$101.30	4.733%	$106.0945	$106.09	$106.10	$106.10
Purchase #4	$130.77	11.839%	$146.2519	$146.25	$146.25	$146.30
Purchase #5	$40.92	5.720%	$43.2606	$43.26	$43.25	$43.30
Purchase #6	$9.87	3.338%	$10.1995	$10.20	$10.20	$10.20
Purchase #7	$130.88	10.381%	$144.4667	$144.47	$144.45	$144.50
7 purchase totals =	$599.52		$650.7632	$650.76	$650.75	$650.90