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	$121.60	3.189%	$125.4778	$125.48	$125.50	$125.50
Purchase #2	$113.52	5.149%	$119.3651	$119.37	$119.35	$119.40
Purchase #3	$214.66	3.427%	$222.0164	$222.02	$222.00	$222.00
Purchase #4	$136.54	9.737%	$149.8349	$149.83	$149.85	$149.80
Purchase #5	$118.48	4.419%	$123.7156	$123.72	$123.70	$123.70
Purchase #6	$234.59	13.210%	$265.5793	$265.58	$265.60	$265.60
Purchase #7	$210.84	5.397%	$222.219	$222.22	$222.20	$222.20
7 purchase totals =	$1,150.23		$1,228.2081	$1,228.22	$1,228.20	$1,228.20