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	$48.72	8.724%	$52.9703	$52.97	$52.95	$53.00
Purchase #2	$99.41	12.162%	$111.5002	$111.50	$111.50	$111.50
Purchase #3	$40.96	4.742%	$42.9023	$42.90	$42.90	$42.90
Purchase #4	$200.67	10.871%	$222.4848	$222.48	$222.50	$222.50
Purchase #5	$248.37	7.189%	$266.2253	$266.23	$266.25	$266.20
Purchase #6	$208.66	5.641%	$220.4305	$220.43	$220.45	$220.40
Purchase #7	$53.71	10.304%	$59.2443	$59.24	$59.25	$59.20
7 purchase totals =	$900.50		$975.7577	$975.75	$975.80	$975.70