My laptop has a display with a native resolution of 1920 x 1080. Windows recommends 125% scaling, which works for most of the other apps I use but makes SONAR Platinum look blurry and reduces my real estate. If I go to 100% scaling in windows, SONAR looks right but other apps go wrong.
 
Here's the solution:
1. Go to the folder where you installed SONAR (in my case c:\Program Files\Cakewalk\SONAR Platinum)
2. Right click on your executable (in my case SONARPLT.exe) and choose 'Properties'
3. Click on the Compatibility tab
4. In the settings section, tick the box entitled 'Disable display scaling on high DPI settings'
5. Click okay.
 
This will allow you to run SONAR at native resolution and your other apps at the scaling recommended by Windows 10.
 
I hope this helps others.

There's a much easier way:
Download and install XPExplorer from here:
http://windows10_dpi_blurry_fix.xpexplorer.com/
Works like a charm.