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	$33.42	13.563%	$37.9528	$37.95	$37.95	$38.00
Purchase #2	$16.87	12.475%	$18.9745	$18.97	$18.95	$19.00
Purchase #3	$172.72	8.541%	$187.472	$187.47	$187.45	$187.50
Purchase #4	$237.46	7.847%	$256.0935	$256.09	$256.10	$256.10
Purchase #5	$245.28	10.674%	$271.4612	$271.46	$271.45	$271.50
Purchase #6	$132.42	10.638%	$146.5068	$146.51	$146.50	$146.50
Purchase #7	$36.81	13.143%	$41.6479	$41.65	$41.65	$41.60
7 purchase totals =	$874.98		$960.1087	$960.10	$960.05	$960.20