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	$100.84	3.854%	$104.7264	$104.73	$104.75	$104.70
Purchase #2	$68.83	5.385%	$72.5365	$72.54	$72.55	$72.50
Purchase #3	$92.94	3.128%	$95.8472	$95.85	$95.85	$95.80
Purchase #4	$183.39	13.515%	$208.1752	$208.18	$208.20	$208.20
Purchase #5	$117.45	8.200%	$127.0809	$127.08	$127.10	$127.10
Purchase #6	$247.97	13.141%	$280.5557	$280.56	$280.55	$280.60
Purchase #7	$15.40	9.534%	$16.8682	$16.87	$16.85	$16.90
7 purchase totals =	$826.82		$905.7901	$905.81	$905.85	$905.80