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	$195.86	6.670%	$208.9239	$208.92	$208.90	$208.90
Purchase #2	$153.60	11.606%	$171.4268	$171.43	$171.45	$171.40
Purchase #3	$37.75	4.617%	$39.4929	$39.49	$39.50	$39.50
Purchase #4	$230.27	11.204%	$256.0695	$256.07	$256.05	$256.10
Purchase #5	$9.71	11.670%	$10.8432	$10.84	$10.85	$10.80
Purchase #6	$100.86	13.276%	$114.2502	$114.25	$114.25	$114.30
Purchase #7	$117.50	13.105%	$132.8984	$132.90	$132.90	$132.90
7 purchase totals =	$845.55		$933.9049	$933.90	$933.90	$933.90