YES

   1: +(0(),x1) -> x1
   2: +(s(x2),x1) -> s(+(x2,x1))
   3: inc(x2) -> s(x2)
   4: +(x2,x1) -> +(x1,x2)
   5: inc(+(x2,x1)) -> +(inc(x2),x1)

@Jouannaud and Kirchner's criterion
--- R
   1: +(0(),x1) -> x1
   2: +(s(x2),x1) -> s(+(x2,x1))
   3: inc(x2) -> s(x2)
   4: +(x2,x1) -> +(x1,x2)
   5: inc(+(x2,x1)) -> +(inc(x2),x1)

--- S
   1: +(0(),x1) -> x1
   2: +(s(x2),x1) -> s(+(x2,x1))
   3: inc(x2) -> s(x2)
   4: +(x2,x1) -> +(x1,x2)
   5: inc(+(x2,x1)) -> +(inc(x2),x1)