Shimano STI 5700 shifter compatibility

I have a 2012 Jamis Quest road bike with the Shimano 105 group. I'm working to change the rear 11-28T cassette for something with lower gearing. The 28T is the lowest offered in the 105 grouping.

I'm trying to figure out which 10 sp. rear derailleur I need to mate up with my current, existing...