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	$168.91	12.110%	$189.365	$189.37	$189.35	$189.40
Purchase #2	$102.29	3.198%	$105.5612	$105.56	$105.55	$105.60
Purchase #3	$249.29	13.291%	$282.4231	$282.42	$282.40	$282.40
Purchase #4	$179.50	4.504%	$187.5847	$187.58	$187.60	$187.60
Purchase #5	$167.67	13.228%	$189.8494	$189.85	$189.85	$189.80
Purchase #6	$124.98	13.105%	$141.3586	$141.36	$141.35	$141.40
Purchase #7	$33.25	3.252%	$34.3313	$34.33	$34.35	$34.30
7 purchase totals =	$1,025.89		$1,130.4733	$1,130.47	$1,130.45	$1,130.50