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	$227.75	12.189%	$255.5104	$255.51	$255.50	$255.50
Purchase #2	$78.82	9.846%	$86.5806	$86.58	$86.60	$86.60
Purchase #3	$179.45	11.443%	$199.9845	$199.98	$200.00	$200.00
Purchase #4	$159.73	5.302%	$168.1989	$168.20	$168.20	$168.20
Purchase #5	$60.56	4.160%	$63.0793	$63.08	$63.10	$63.10
Purchase #6	$246.81	6.160%	$262.0135	$262.01	$262.00	$262.00
Purchase #7	$117.56	12.614%	$132.389	$132.39	$132.40	$132.40
7 purchase totals =	$1,070.68		$1,167.7562	$1,167.75	$1,167.80	$1,167.80