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	$157.96	4.844%	$165.6116	$165.61	$165.60	$165.60
Purchase #2	$203.66	10.734%	$225.5209	$225.52	$225.50	$225.50
Purchase #3	$45.41	5.395%	$47.8599	$47.86	$47.85	$47.90
Purchase #4	$53.75	4.636%	$56.2419	$56.24	$56.25	$56.20
Purchase #5	$199.38	11.741%	$222.7892	$222.79	$222.80	$222.80
Purchase #6	$147.98	9.189%	$161.5779	$161.58	$161.60	$161.60
Purchase #7	$77.48	6.870%	$82.8029	$82.80	$82.80	$82.80
7 purchase totals =	$885.62		$962.4043	$962.40	$962.40	$962.40