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	$150.83	5.295%	$158.8164	$158.82	$158.80	$158.80
Purchase #2	$97.25	5.327%	$102.4305	$102.43	$102.45	$102.40
Purchase #3	$38.78	10.803%	$42.9694	$42.97	$42.95	$43.00
Purchase #4	$112.95	6.291%	$120.0557	$120.06	$120.05	$120.10
Purchase #5	$38.79	4.665%	$40.5996	$40.60	$40.60	$40.60
Purchase #6	$64.52	10.785%	$71.4785	$71.48	$71.50	$71.50
Purchase #7	$214.44	12.697%	$241.6674	$241.67	$241.65	$241.70
7 purchase totals =	$717.56		$778.0175	$778.03	$778.00	$778.10