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	$183.63	9.187%	$200.5001	$200.50	$200.50	$200.50
Purchase #2	$160.62	6.420%	$170.9318	$170.93	$170.95	$170.90
Purchase #3	$177.61	5.789%	$187.8918	$187.89	$187.90	$187.90
Purchase #4	$191.52	13.652%	$217.6663	$217.67	$217.65	$217.70
Purchase #5	$187.86	4.659%	$196.6124	$196.61	$196.60	$196.60
Purchase #6	$47.37	3.249%	$48.9091	$48.91	$48.90	$48.90
Purchase #7	$15.75	13.702%	$17.9081	$17.91	$17.90	$17.90
7 purchase totals =	$964.36		$1,040.4196	$1,040.42	$1,040.40	$1,040.40