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	$62.46	6.259%	$66.3694	$66.37	$66.35	$66.40
Purchase #2	$86.33	9.528%	$94.5555	$94.56	$94.55	$94.60
Purchase #3	$20.49	5.298%	$21.5756	$21.58	$21.60	$21.60
Purchase #4	$99.95	12.475%	$112.4188	$112.42	$112.40	$112.40
Purchase #5	$239.93	13.580%	$272.5125	$272.51	$272.50	$272.50
Purchase #6	$208.53	6.476%	$222.0344	$222.03	$222.05	$222.00
Purchase #7	$244.63	5.141%	$257.2064	$257.21	$257.20	$257.20
7 purchase totals =	$962.32		$1,046.6726	$1,046.68	$1,046.65	$1,046.70