All updates start here and select product, read to see if you need to install updates in number order, or if the updates are cumulative for the individual product http://www.adobe.com/downloads/updates/
The D810 requires Camera Raw 8.6 or newer. None of those versions of Camera Raw are compatible with Photoshop CS5. Your choices are:
1. Subscribe to the creative cloud photography plan and get the latest Photoshop and Lightroom ($9.99/month).
2. Download and install the latest DNG converter and create DNG copies of your NEF files.
3. Add Lightroom to your workflow. Lightroom 6 standalone can be purchased.
There isn't a "recent" CS5 update because it has been a discontinued product since 2012.
Any Camera Raw updates will only be supported by current products, which include CS6 and CC.