If you right click on a file, open the details, you can calculate several checksums. However, you may calculate all checksums at once, simply by clicking on the buttons. 

In case you got a large file or a slow HDD, this may take a while. 
If you accidentially started a calculation, you may stop it by closing the dialog.

However, if you already started one type of calculation and you accidentally hit another button to calculate a different checksum, you are can't simply disrupt either one. You need to wait until both calculation have finished or stop both by closing the dialog.

Therefore a button to stop or pause a specific checksum calculation would be very convenient.