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	$206.43	9.245%	$225.5145	$225.51	$225.50	$225.50
Purchase #2	$74.97	13.119%	$84.8053	$84.81	$84.80	$84.80
Purchase #3	$40.25	8.485%	$43.6652	$43.67	$43.65	$43.70
Purchase #4	$73.41	12.538%	$82.6141	$82.61	$82.60	$82.60
Purchase #5	$208.28	11.208%	$231.624	$231.62	$231.60	$231.60
Purchase #6	$59.83	3.800%	$62.1035	$62.10	$62.10	$62.10
Purchase #7	$172.49	8.163%	$186.5704	$186.57	$186.55	$186.60
7 purchase totals =	$835.66		$916.8970	$916.89	$916.80	$916.90