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	$204.33	11.501%	$227.83	$227.83	$227.85	$227.80
Purchase #2	$128.60	9.105%	$140.309	$140.31	$140.30	$140.30
Purchase #3	$52.90	13.377%	$59.9764	$59.98	$60.00	$60.00
Purchase #4	$242.55	7.542%	$260.8431	$260.84	$260.85	$260.80
Purchase #5	$63.66	4.239%	$66.3585	$66.36	$66.35	$66.40
Purchase #6	$241.31	13.506%	$273.9013	$273.90	$273.90	$273.90
Purchase #7	$178.77	4.256%	$186.3785	$186.38	$186.40	$186.40
7 purchase totals =	$1,112.12		$1,215.5968	$1,215.60	$1,215.65	$1,215.60