Validation Error: PayPal amounts do not match

This plugin works well as a way to allow me to sell .5 amounts of my products. However, the plugin is not passing the correct final price amount to paypal, it is rounding down to the nearest whole integer.

For example, I have a product that is $18/lb. Customer orders 1.5 lbs and is charged $27 in WordPress, but only $18 is passed onto PayPal. Because PayPal is looking for $18 but the order is for $27, the transaction changes from Pending Payment to On Hold.

Please advise – thanks!