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	$66.62	8.697%	$72.4139	$72.41	$72.40	$72.40
Purchase #2	$28.71	13.171%	$32.4914	$32.49	$32.50	$32.50
Purchase #3	$83.70	3.466%	$86.601	$86.60	$86.60	$86.60
Purchase #4	$87.82	9.161%	$95.8652	$95.87	$95.85	$95.90
Purchase #5	$129.37	11.145%	$143.7883	$143.79	$143.80	$143.80
Purchase #6	$143.29	12.693%	$161.4778	$161.48	$161.50	$161.50
Purchase #7	$155.73	13.525%	$176.7925	$176.79	$176.80	$176.80
7 purchase totals =	$695.24		$769.4301	$769.43	$769.45	$769.50