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	$35.46	8.458%	$38.4592	$38.46	$38.45	$38.50
Purchase #2	$198.56	9.264%	$216.9546	$216.95	$216.95	$217.00
Purchase #3	$244.39	5.778%	$258.5109	$258.51	$258.50	$258.50
Purchase #4	$72.60	11.604%	$81.0245	$81.02	$81.00	$81.00
Purchase #5	$67.43	7.462%	$72.4616	$72.46	$72.45	$72.50
Purchase #6	$84.75	6.318%	$90.1045	$90.10	$90.10	$90.10
Purchase #7	$12.57	11.638%	$14.0329	$14.03	$14.05	$14.00
7 purchase totals =	$715.76		$771.5482	$771.53	$771.50	$771.60