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	$7.97	7.766%	$8.589	$8.59	$8.60	$8.60
Purchase #2	$34.34	10.477%	$37.9378	$37.94	$37.95	$37.90
Purchase #3	$225.69	13.236%	$255.5623	$255.56	$255.55	$255.60
Purchase #4	$32.96	6.198%	$35.0029	$35.00	$35.00	$35.00
Purchase #5	$204.84	5.746%	$216.6101	$216.61	$216.60	$216.60
Purchase #6	$169.40	4.196%	$176.508	$176.51	$176.50	$176.50
Purchase #7	$60.72	9.165%	$66.285	$66.29	$66.30	$66.30
7 purchase totals =	$735.92		$796.4951	$796.50	$796.50	$796.50