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	$41.41	12.438%	$46.5606	$46.56	$46.55	$46.60
Purchase #2	$126.52	12.193%	$141.9466	$141.95	$141.95	$141.90
Purchase #3	$129.51	12.411%	$145.5835	$145.58	$145.60	$145.60
Purchase #4	$76.68	11.410%	$85.4292	$85.43	$85.45	$85.40
Purchase #5	$187.64	9.256%	$205.008	$205.01	$205.00	$205.00
Purchase #6	$77.47	7.454%	$83.2446	$83.24	$83.25	$83.20
Purchase #7	$80.46	3.832%	$83.5432	$83.54	$83.55	$83.50
7 purchase totals =	$719.69		$791.3157	$791.31	$791.35	$791.20