CoercionShaman
We have professional grade monitors at work that I was referring to.  Some systems run the Quadro cards, others the 'normal' cards.  It works on the 'normal' cards as well.  Probably not something that is in most homes because of the prices.
 
My Dell U3415W allows me to select it, but it is actually 8 bit with dithering, so I don't know if there is actually any real benefit.

can you get permission to test geforce cards in the actual 10 bit monitor?

Nvidia consumer class cards (Geforce GTX) can only output 10 bit color in a Direct X11 exclusive fullscreen mode. To get 10 bit color output on the Desktop in a way professional applications use it you need a Quadro card and drivers. Nvidia is blocking this for Geforce cards, regardless of the control panel setting a Geforce card will not process/output proper 10 bit color output. Anyone in doubt just try this tool:
 
http://www.necdisplay.com/documents/Software/NEC_10_bit_video_Windows_demo.zip
 
Works with my Quadro M5000, fails with my GTX1080. Same PC, a NEC SpectraView Reference 322UHD-2 as Monitor.
 
To test 10 bit output in DX11 exclusive fullscreen you can try this:
 
http://forum.doom9.org/showthread.php?t=172128
 
Games that I know that can render in 10 bit with a Geforce card if your Monitor supports it:
 
GRID 2, GRID Autosport, Alien: Isolation. There may be more now.
 

I guess that answers that with certainty.
 
The only users at work that would probably be able to truly notice any difference all have the Quadro cards anyway.

Only workstation cards output true 10 bit color for both Direct X and OpenGL. Geforce cards will support 8+2 dithered in some applications. At least this is the case for 900 series and below.
 
As far as Pascal goes. It will support 10/12 bit color in Direct X driven applications however OpenGL will still use 8 bit color. You will still need a Quadro with workstation drivers to achieve 10 bit in OpenGL.

MilenaM
Nvidia consumer class cards (Geforce GTX) can only output 10 bit color in a Direct X11 exclusive fullscreen mode. To get 10 bit color output on the Desktop in a way professional applications use it you need a Quadro card and drivers. Nvidia is blocking this for Geforce cards, regardless of the control panel setting a Geforce card will not process/output proper 10 bit color output. Anyone in doubt just try this tool:
 
http://www.necdisplay.com/documents/Software/NEC_10_bit_video_Windows_demo.zip
 
Works with my Quadro M5000, fails with my GTX1080. Same PC, a NEC SpectraView Reference 322UHD-2 as Monitor.
 
To test 10 bit output in DX11 exclusive fullscreen you can try this:
 
http://forum.doom9.org/showthread.php?t=172128
 
Games that I know that can render in 10 bit with a Geforce card if your Monitor supports it:
 
GRID 2, GRID Autosport, Alien: Isolation. There may be more now.
 

is there a hack for 10 bit output?

STR8_AN94BALLER
 
is there a hack for 10 bit output?

+1
It works with DisplayPort but not over HDMI.  I can't imagine nobody has found a way around this limitation on hardware that's obviously capable...  I'm not surprised by NVIDIA pulling a stunt like this.

Latest EVGA 1080ti FE card DOES NOT have 10 bit options for latest XB271HK 4K 10bit IPS monitor. I am using latest DP cable. I simply can't get 10 bit to show up no matter what I tried.
 
So, only Quaddro support 10bit or "regular" cards do to ? I mean does anyone actually KNOW ?