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	$13.69	12.437%	$15.3926	$15.39	$15.40	$15.40
Purchase #2	$7.94	11.638%	$8.8641	$8.86	$8.85	$8.90
Purchase #3	$37.25	4.540%	$38.9412	$38.94	$38.95	$38.90
Purchase #4	$208.70	3.802%	$216.6348	$216.63	$216.65	$216.60
Purchase #5	$239.97	13.128%	$271.4733	$271.47	$271.45	$271.50
Purchase #6	$87.30	11.697%	$97.5115	$97.51	$97.50	$97.50
Purchase #7	$35.58	5.698%	$37.6073	$37.61	$37.60	$37.60
7 purchase totals =	$630.43		$686.4248	$686.41	$686.40	$686.40