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	$167.70	10.143%	$184.7098	$184.71	$184.70	$184.70
Purchase #2	$125.71	13.105%	$142.1843	$142.18	$142.20	$142.20
Purchase #3	$164.66	4.825%	$172.6048	$172.60	$172.60	$172.60
Purchase #4	$180.92	8.664%	$196.5949	$196.59	$196.60	$196.60
Purchase #5	$239.29	12.495%	$269.1893	$269.19	$269.20	$269.20
Purchase #6	$250.58	13.544%	$284.5186	$284.52	$284.50	$284.50
Purchase #7	$196.49	11.583%	$219.2494	$219.25	$219.25	$219.20
7 purchase totals =	$1,325.35		$1,469.0511	$1,469.04	$1,469.05	$1,469.00