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	$92.81	11.756%	$103.7207	$103.72	$103.70	$103.70
Purchase #2	$198.90	12.561%	$223.8838	$223.88	$223.90	$223.90
Purchase #3	$227.35	6.542%	$242.2232	$242.22	$242.20	$242.20
Purchase #4	$21.32	11.638%	$23.8012	$23.80	$23.80	$23.80
Purchase #5	$113.70	4.193%	$118.4674	$118.47	$118.45	$118.50
Purchase #6	$88.93	13.145%	$100.6198	$100.62	$100.60	$100.60
Purchase #7	$134.65	5.116%	$141.5387	$141.54	$141.55	$141.50
7 purchase totals =	$877.66		$954.2548	$954.25	$954.20	$954.20