https://tex.stackexchange.com/q/434622/35864

bobbooktabs.tex

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{booktabs}
\usepackage{siunitx}

\begin{document}
\begin{table}
  \centering
  \caption{Example} \label{tab:title} 
  \begin{tabular}{S[table-format=2.0]S[table-format=3.0]S[table-format=1.2e-1]S[table-format=1.7]S[table-format=1.2]}
    \toprule
     {Iter.} & {$N$} &  {$\epsilon$} & {$J = r_{f}$} & {CPU (sec)}\\
    \midrule
      0 &   7 & 9.71e-3 & 1.0125612 & 0.21 \\ 
      1 &  13 & 1.01e-3 & 1.0125873 & 0.13 \\
      2 &  16 & 8.74e-4 & 1.0126011 & 0.79 \\ 
      3 &  21 & 5.32e-4 & 1.0126056 & 1.03 \\  
      4 &  30 & 3.21e-4 & 1.0126099 & 2.34 \\  
      5 &  36 & 9.82e-5 & 1.0127022 & 1.64 \\  
      6 &  45 & 5.19e-5 & 1.0127067 & 1.19 \\  
      7 &  64 & 4.70e-5 & 1.0127143 & 2.15 \\  
      8 &  80 & 7.57e-6 & 1.0127156 & 3.10 \\  
      9 &  99 & 8.73e-6 & 1.0127174 & 6.56 \\  
     10 & 165 & 9.80e-7 & 1.0127176 & 7.98 \\  
    \bottomrule
  \end{tabular}
\end{table}
\end{document}