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	$79.61	8.666%	$86.509	$86.51	$86.50	$86.50
Purchase #2	$63.59	12.683%	$71.6551	$71.66	$71.65	$71.70
Purchase #3	$92.77	11.491%	$103.4302	$103.43	$103.45	$103.40
Purchase #4	$241.38	8.698%	$262.3752	$262.38	$262.40	$262.40
Purchase #5	$164.57	12.624%	$185.3453	$185.35	$185.35	$185.30
Purchase #6	$66.88	10.868%	$74.1485	$74.15	$74.15	$74.10
Purchase #7	$126.82	9.574%	$138.9617	$138.96	$138.95	$139.00
7 purchase totals =	$835.62		$922.4250	$922.44	$922.45	$922.40