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	$130.84	11.509%	$145.8984	$145.90	$145.90	$145.90
Purchase #2	$239.66	8.302%	$259.5566	$259.56	$259.55	$259.60
Purchase #3	$99.93	5.443%	$105.3692	$105.37	$105.35	$105.40
Purchase #4	$207.51	5.181%	$218.2611	$218.26	$218.25	$218.30
Purchase #5	$111.40	10.497%	$123.0937	$123.09	$123.10	$123.10
Purchase #6	$69.66	12.476%	$78.3508	$78.35	$78.35	$78.40
Purchase #7	$144.70	12.657%	$163.0147	$163.01	$163.00	$163.00
7 purchase totals =	$1,003.70		$1,093.5445	$1,093.54	$1,093.50	$1,093.70