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	$62.25	6.661%	$66.3965	$66.40	$66.40	$66.40
Purchase #2	$222.32	5.816%	$235.2501	$235.25	$235.25	$235.30
Purchase #3	$99.25	3.249%	$102.4746	$102.47	$102.45	$102.50
Purchase #4	$247.54	3.622%	$256.5059	$256.51	$256.50	$256.50
Purchase #5	$31.33	11.554%	$34.9499	$34.95	$34.95	$34.90
Purchase #6	$124.75	9.371%	$136.4403	$136.44	$136.45	$136.40
Purchase #7	$9.48	10.140%	$10.4413	$10.44	$10.45	$10.40
7 purchase totals =	$796.92		$842.4586	$842.46	$842.45	$842.40