The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -2.2974\\[1 em]x_2 &= 1.8586+1.3504i\\[1 em]x_3 &= 1.8586-1.3504i\\[1 em]x_4 &= -0.7099+2.185i\\[1 em]x_5 &= -0.7099-2.185i \end{aligned} $$Polynomial $ x^5+64 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.