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	$126.59	10.268%	$139.5883	$139.59	$139.60	$139.60
Purchase #2	$111.71	7.340%	$119.9095	$119.91	$119.90	$119.90
Purchase #3	$73.47	4.638%	$76.8775	$76.88	$76.90	$76.90
Purchase #4	$128.89	6.210%	$136.8941	$136.89	$136.90	$136.90
Purchase #5	$239.96	13.743%	$272.9377	$272.94	$272.95	$272.90
Purchase #6	$109.88	11.683%	$122.7173	$122.72	$122.70	$122.70
Purchase #7	$221.67	11.809%	$247.847	$247.85	$247.85	$247.80
7 purchase totals =	$1,012.17		$1,116.7714	$1,116.78	$1,116.80	$1,116.70