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	$194.76	11.149%	$216.4738	$216.47	$216.45	$216.50
Purchase #2	$144.68	4.326%	$150.9389	$150.94	$150.95	$150.90
Purchase #3	$214.71	13.779%	$244.2949	$244.29	$244.30	$244.30
Purchase #4	$232.40	8.171%	$251.3894	$251.39	$251.40	$251.40
Purchase #5	$181.50	13.111%	$205.2965	$205.30	$205.30	$205.30
Purchase #6	$43.43	12.642%	$48.9204	$48.92	$48.90	$48.90
Purchase #7	$125.82	9.431%	$137.6861	$137.69	$137.70	$137.70
7 purchase totals =	$1,137.30		$1,255.0000	$1,255.00	$1,255.00	$1,255.00