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	$67.65	8.698%	$73.5342	$73.53	$73.55	$73.50
Purchase #2	$77.67	9.533%	$85.0743	$85.07	$85.05	$85.10
Purchase #3	$172.81	10.486%	$190.9309	$190.93	$190.95	$190.90
Purchase #4	$59.70	11.133%	$66.3464	$66.35	$66.35	$66.30
Purchase #5	$117.42	5.176%	$123.4977	$123.50	$123.50	$123.50
Purchase #6	$35.75	12.602%	$40.2552	$40.26	$40.25	$40.30
Purchase #7	$192.65	9.868%	$211.6607	$211.66	$211.65	$211.70
7 purchase totals =	$723.65		$791.2994	$791.30	$791.30	$791.30