Benutzerdefiniertes Grid in pgfplots

\documentclass[11pt,a4paper,oneside,chapterprefix,numbers=enddot]{scrbook}
\usepackage{pgfplots,siunitx}                       
\pgfplotsset{width=\textwidth, height = 0.4\textheight,
compat=newest, minor tick style={black}, legend style={cells={anchor=west}},every axis legend/.append style={at={(0.99,0.02)},anchor=south east}, ticklabel shift={0.05cm}}
\usepgfplotslibrary{units}

\begin{document}
\begin{figure}
\begin{minipage}[t]{0.475\textwidth}
\centering
   \begin{tikzpicture}
      \begin{axis}[grid = major,
                xlabel near ticks,
                ylabel near ticks,
                xlabel = {Zeit} \si{\minute},
                ylabel = {Temperatur} \si{\celsius},
                xtick = {0,100},
                xmin=-10, xmax=110,
                ]
         \addplot[blue,mark=none,domain=0:100, samples=2]    {10*x};
      \end{axis}
         \end{tikzpicture}
      \caption{Nr.1}
\end{minipage}
      \hfill
\begin{minipage}[t]{0.475\textwidth}
\centering
   \begin{tikzpicture}
      \begin{axis}[grid = major,
        width=\textwidth,height=.5\textheight,% Übersteuere \pgfplotsset
                xlabel near ticks,
                ylabel near ticks,
                xlabel = {x},
                ylabel = {y},
                xtick = {0,80},
                xmin=-10, xmax=110,
                ymax=1100 ]
         \addplot[blue,mark=none,domain=0:80, samples=2] {10*x};
      \draw[xstep=10,ystep=100,gray,very thin] (-10,-100) grid (110,1100); % individuelles GRID eingefügt
      \end{axis}
         \end{tikzpicture}
             \caption{Nr.2}
\end{minipage}
      \end{figure}

\end{document}