Monospaced numbers in invoice2

Question

I am trying to make an invoice where the entries are all using ttfamily, in the invoice2 package, but can't seem to get the numbers (as opposed to the table text) in monospace. This is frustrating as it is especially the numbers I want monospaced. How can I get the table to be entirely (or even just for the numbers!) in ttfamily?

A minimum example, where the problem is apparent:

\documentclass{article}
\usepackage{times}
\usepackage{invoice2}
\usepackage{eurosym}
\begin{document}
\ttfamily
 \invoiceoptions{vat=.09}
 \begin{invoice}[currency-symbol={\euro{}}]
 \ttfamily
    \invoicesingleitem{Ignition!}{4087.99}
    \invoiceitem{1.5}{The Art of Computer Programming 1--4}{162.99}
    \invoiceitem{20}{The TeXbook}{55.69}
 \end{invoice}
\end{document}

Answer 1

The invoice2 package internally uses the siunitx package to format numbers. If you want to change the font of the numbers you can use siunitx settings, with the command \sisetup.

The settings are described in the siunitx manual on page 18. The default mode for numbers is math, which means you can influence the number font by setting the math-rm option, in this case to \mathtt.

MWE:

\documentclass{article}
\usepackage{times}
\usepackage{invoice2}
\sisetup{math-rm = \mathtt}
\usepackage{eurosym}
\begin{document}
 \invoiceoptions{vat=.09}
 \begin{invoice}[currency-symbol={\euro{}}]
    \invoicesingleitem{Ignition!}{4087.99}
    \invoiceitem{1.5}{The Art of Computer Programming 1--4}{162.99}
    \invoiceitem{20}{The TeXbook}{55.69}
 \end{invoice}
\end{document}

Result:

If you prefer the Times monospace font then you can also use \sisetup{math-rm = \texttt}: