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	$221.80	5.527%	$234.0589	$234.06	$234.05	$234.10
Purchase #2	$119.43	3.348%	$123.4285	$123.43	$123.45	$123.40
Purchase #3	$204.47	5.160%	$215.0207	$215.02	$215.00	$215.00
Purchase #4	$53.56	12.120%	$60.0515	$60.05	$60.05	$60.10
Purchase #5	$85.93	5.314%	$90.4963	$90.50	$90.50	$90.50
Purchase #6	$57.74	10.659%	$63.8945	$63.89	$63.90	$63.90
Purchase #7	$208.60	11.102%	$231.7588	$231.76	$231.75	$231.80
7 purchase totals =	$951.53		$1,018.7092	$1,018.71	$1,018.70	$1,018.80