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	$126.65	13.154%	$143.3095	$143.31	$143.30	$143.30
Purchase #2	$151.51	7.495%	$162.8657	$162.87	$162.85	$162.90
Purchase #3	$29.83	7.369%	$32.0282	$32.03	$32.05	$32.00
Purchase #4	$228.39	5.243%	$240.3645	$240.36	$240.35	$240.40
Purchase #5	$49.76	3.105%	$51.305	$51.31	$51.30	$51.30
Purchase #6	$127.43	7.866%	$137.4536	$137.45	$137.45	$137.50
Purchase #7	$249.46	10.439%	$275.5011	$275.50	$275.50	$275.50
7 purchase totals =	$963.03		$1,042.8276	$1,042.83	$1,042.80	$1,042.90