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	$146.80	9.428%	$160.6403	$160.64	$160.65	$160.60
Purchase #2	$157.43	5.140%	$165.5219	$165.52	$165.50	$165.50
Purchase #3	$146.78	8.855%	$159.7774	$159.78	$159.80	$159.80
Purchase #4	$154.62	9.856%	$169.8593	$169.86	$169.85	$169.90
Purchase #5	$108.77	3.397%	$112.4649	$112.46	$112.45	$112.50
Purchase #6	$65.76	9.853%	$72.2393	$72.24	$72.25	$72.20
Purchase #7	$71.44	6.509%	$76.09	$76.09	$76.10	$76.10
7 purchase totals =	$851.60		$916.5931	$916.59	$916.60	$916.60