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	$160.91	12.517%	$181.0511	$181.05	$181.05	$181.10
Purchase #2	$94.54	11.626%	$105.5312	$105.53	$105.55	$105.50
Purchase #3	$164.61	10.295%	$181.5566	$181.56	$181.55	$181.60
Purchase #4	$40.67	3.248%	$41.991	$41.99	$42.00	$42.00
Purchase #5	$33.34	3.764%	$34.5949	$34.59	$34.60	$34.60
Purchase #6	$216.98	8.509%	$235.4428	$235.44	$235.45	$235.40
Purchase #7	$235.54	6.549%	$250.9655	$250.97	$250.95	$251.00
7 purchase totals =	$946.59		$1,031.1331	$1,031.13	$1,031.15	$1,031.20