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	$53.43	9.682%	$58.6031	$58.60	$58.60	$58.60
Purchase #2	$102.38	8.538%	$111.1212	$111.12	$111.10	$111.10
Purchase #3	$59.52	3.307%	$61.4883	$61.49	$61.50	$61.50
Purchase #4	$210.77	5.563%	$222.4951	$222.50	$222.50	$222.50
Purchase #5	$207.71	6.662%	$221.5476	$221.55	$221.55	$221.50
Purchase #6	$17.98	11.254%	$20.0035	$20.00	$20.00	$20.00
Purchase #7	$123.70	5.291%	$130.245	$130.25	$130.25	$130.20
7 purchase totals =	$775.49		$825.5038	$825.51	$825.50	$825.40