How can I cut and paste entries from the Calculator when entering Closing amounts for non-cash entries such as Checks?

Once your calculation is complete, press Ctrl-C for Copy (or click on the middle icon in the toolbar of the Calculator).
Close the Calculator.
Click the tender entry box you want to enter.
Press F2(edit mode) or the Spacebar.
Press Ctrl-V for Paste (or right-click and select Paste).