On a D20 roll a +1 modifier equals +5%. What percentage would +1 add to 2D10, 3D10 and 4D10?

I have been reading about replacing the D20 in Dnd with 3D6.

One of the criticisms was that modifiers are exaggerated when you use 3D6, with some people saying a +1 modifier acts more like a +10% modifier.

What would be the percentage modifier of a +1 modifier on various numbers of D10 rolls and how would you calculate that?