YES

1 decompositions
 #1 -----------
   1: f(g(g(x1))) -> a()
   2: f(g(h(x2))) -> b()
   3: f(h(g(x3))) -> b()
   4: f(h(h(x4))) -> c()
   5: g(x5) -> h(x5)
   6: a() -> b()
   7: b() -> c()

@Knuth and Bendix' criterion
--- R
   1: f(g(g(x1))) -> a()
   2: f(g(h(x2))) -> b()
   3: f(h(g(x3))) -> b()
   4: f(h(h(x4))) -> c()
   5: g(x5) -> h(x5)
   6: a() -> b()
   7: b() -> c()

--- S
   1: f(g(g(x1))) -> a()
   2: f(g(h(x2))) -> b()
   3: f(h(g(x3))) -> b()
   4: f(h(h(x4))) -> c()
   5: g(x5) -> h(x5)
   6: a() -> b()
   7: b() -> c()