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	$175.62	13.784%	$199.8275	$199.83	$199.85	$199.80
Purchase #2	$71.80	13.421%	$81.4363	$81.44	$81.45	$81.40
Purchase #3	$227.27	4.200%	$236.8153	$236.82	$236.80	$236.80
Purchase #4	$87.56	3.528%	$90.6491	$90.65	$90.65	$90.60
Purchase #5	$37.42	13.806%	$42.5862	$42.59	$42.60	$42.60
Purchase #6	$48.34	13.577%	$54.9031	$54.90	$54.90	$54.90
Purchase #7	$150.41	6.691%	$160.4739	$160.47	$160.45	$160.50
7 purchase totals =	$798.42		$866.6914	$866.70	$866.70	$866.60