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	$164.28	9.438%	$179.7847	$179.78	$179.80	$179.80
Purchase #2	$69.38	9.754%	$76.1473	$76.15	$76.15	$76.10
Purchase #3	$160.31	7.647%	$172.5689	$172.57	$172.55	$172.60
Purchase #4	$44.66	4.750%	$46.7814	$46.78	$46.80	$46.80
Purchase #5	$216.31	3.776%	$224.4779	$224.48	$224.50	$224.50
Purchase #6	$78.76	8.758%	$85.6578	$85.66	$85.65	$85.70
Purchase #7	$177.76	3.600%	$184.1594	$184.16	$184.15	$184.20
7 purchase totals =	$911.46		$969.5774	$969.58	$969.60	$969.70