\documentclass[a4paper]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[locale=DE]{siunitx}
\usepackage{datatool}
\usepackage{booktabs}
\renewcommand{\dtldisplaystarttab}{\toprule}
\renewcommand{\dtldisplayafterhead}{\midrule}
\renewcommand{\dtldisplayendtab}{\\\bottomrule}
\sisetup{
round-mode = places,
round-precision = 2,
}
\begin{document}
\DTLloaddb{stores}{messergebnisse.csv}
\DTLdisplaydb{stores}
\end{document}