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	$199.57	8.129%	$215.793	$215.79	$215.80	$215.80
Purchase #2	$242.33	12.446%	$272.4904	$272.49	$272.50	$272.50
Purchase #3	$27.90	13.382%	$31.6336	$31.63	$31.65	$31.60
Purchase #4	$145.51	9.174%	$158.8591	$158.86	$158.85	$158.90
Purchase #5	$168.79	10.514%	$186.5366	$186.54	$186.55	$186.50
Purchase #6	$128.78	8.419%	$139.622	$139.62	$139.60	$139.60
Purchase #7	$240.61	11.802%	$269.0068	$269.01	$269.00	$269.00
7 purchase totals =	$1,153.49		$1,273.9415	$1,273.94	$1,273.95	$1,273.90