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	$116.94	12.341%	$131.3716	$131.37	$131.35	$131.40
Purchase #2	$114.47	6.138%	$121.4962	$121.50	$121.50	$121.50
Purchase #3	$146.85	13.250%	$166.3076	$166.31	$166.30	$166.30
Purchase #4	$37.97	11.468%	$42.3244	$42.32	$42.30	$42.30
Purchase #5	$35.48	3.511%	$36.7257	$36.73	$36.75	$36.70
Purchase #6	$33.60	9.248%	$36.7073	$36.71	$36.70	$36.70
Purchase #7	$220.25	3.317%	$227.5557	$227.56	$227.55	$227.60
7 purchase totals =	$705.56		$762.4885	$762.50	$762.45	$762.50