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	$223.48	11.244%	$248.6081	$248.61	$248.60	$248.60
Purchase #2	$59.66	5.795%	$63.1173	$63.12	$63.10	$63.10
Purchase #3	$239.57	8.137%	$259.0638	$259.06	$259.05	$259.10
Purchase #4	$102.25	3.262%	$105.5854	$105.59	$105.60	$105.60
Purchase #5	$14.45	7.858%	$15.5855	$15.59	$15.60	$15.60
Purchase #6	$226.62	13.273%	$256.6993	$256.70	$256.70	$256.70
Purchase #7	$204.32	5.628%	$215.8191	$215.82	$215.80	$215.80
7 purchase totals =	$1,070.35		$1,164.4785	$1,164.49	$1,164.45	$1,164.50