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	$76.70	13.373%	$86.9571	$86.96	$86.95	$87.00
Purchase #2	$95.48	8.509%	$103.6044	$103.60	$103.60	$103.60
Purchase #3	$128.81	9.777%	$141.4038	$141.40	$141.40	$141.40
Purchase #4	$50.71	6.263%	$53.886	$53.89	$53.90	$53.90
Purchase #5	$52.50	4.569%	$54.8987	$54.90	$54.90	$54.90
Purchase #6	$103.61	12.798%	$116.87	$116.87	$116.85	$116.90
Purchase #7	$244.42	6.116%	$259.3687	$259.37	$259.35	$259.40
7 purchase totals =	$752.23		$816.9887	$816.99	$816.95	$817.10