Negative locations show as the negative location +1
When teleporting to a positive location (/tp 5 4 5) you are told you have been teleported to 5.5, 4, 5.5
When teleporting to a negative location (/tp -5 4 5) you are told you have been teleported to -4.5, 4, 5.5
I can confirm this is the same on singleplayer and on servers.
This currently affects my (modified)server as the wrong location being reported causes invisible borders to be out of place.
This is how coordinates work. -0 and +0 are the same position; -1 is 1 unit away from 0. Add +.5 to get the center of the block, and the block at -1 is centered at -.5, the block at 0 is centered at +.5, the block at 1 is centered at +1.5, etc. See MC-4794 for more information.