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	$160.59	3.872%	$166.808	$166.81	$166.80	$166.80
Purchase #2	$172.82	5.706%	$182.6811	$182.68	$182.70	$182.70
Purchase #3	$78.83	12.546%	$88.72	$88.72	$88.70	$88.70
Purchase #4	$144.74	11.831%	$161.8642	$161.86	$161.85	$161.90
Purchase #5	$139.29	5.656%	$147.1682	$147.17	$147.15	$147.20
Purchase #6	$21.87	12.688%	$24.6449	$24.64	$24.65	$24.60
Purchase #7	$167.38	13.589%	$190.1253	$190.13	$190.15	$190.10
7 purchase totals =	$885.52		$962.0117	$962.01	$962.00	$962.00