Main toolbar > Percent Snap Toggle
Keyboard > Ctrl+Shift+P
Percent Snap Toggle increments scaling of objects by the specified percentage.
The snap percent increment is set in the Grid And Snap Settings dialog. The default is 10 percent. Right-click the Percent Snap Toggle button to display the Grid and Snap Settings dialog.
This is a general-purpose snap system that applies to any operation involving a percentage, such as scaling or squashing.