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	$132.39	9.484%	$144.9459	$144.95	$144.95	$144.90
Purchase #2	$49.78	5.641%	$52.5881	$52.59	$52.60	$52.60
Purchase #3	$34.91	10.407%	$38.5431	$38.54	$38.55	$38.50
Purchase #4	$15.48	13.424%	$17.558	$17.56	$17.55	$17.60
Purchase #5	$207.79	11.175%	$231.0105	$231.01	$231.00	$231.00
Purchase #6	$173.45	3.265%	$179.1131	$179.11	$179.10	$179.10
Purchase #7	$146.61	8.292%	$158.7669	$158.77	$158.75	$158.80
7 purchase totals =	$760.41		$822.5256	$822.53	$822.50	$822.50