Implement two-digit-rounding (with uncertainty) in LaTeX using siunitx

Based on my very limited knowledge of TeX (and searching the Internet) I came up with the following solution which I will provide here as a start for others to improve on this:

documentclass{minimal}

usepackage{siunitx}
usepackage{stringstrings}

newcommand*{numRF}[2]{num[round-mode=figures,round-precision=#2]{#1}}

begin{document}

  newcommand{matchroundtabular}[2]{% only works for integer values
    {%
    aftergroupround
    stringlength[q]{#1}
    newcountnumlen
    numlen=theresult
    stringlength[q]{#2}
    newcounterrorlen
    errorlen=theresult
    newcountround
    round=numlen
    advanceround by -errorlen
    advanceround by 1
    expandafter
    }
    theround
    {numRF{#1}{round}} & {numRF{#2}{2}}%
  }

  % Problem 1: alignment off  
  sisetup{round-mode = figures,round-precision = 2, table-number-alignment = right}%
  begin{tabular}{
    l
    S[table-format=6.0]@{$,pm,$}S[table-format=3.0]@{~}
    S[table-format=6.0]@{$,pm,$}S[table-format=3.0]@{~}
  }
    2 tight $tau$s     & matchroundtabular{72293}{269}     &    80839 &   51 
    2 medium $tau$s    & matchroundtabular{212383}{461}    &   231155 &  125 
  end{tabular}

  % Problem 2: not working here
  begin{tabular}{c@{$,pm,$}c}
    Aaaaa & Bbbbb 
    matchroundtabular{343454}{455}
  end{tabular}

end{document}

Output:

So this works but has two problems:

1. The alignment is off. (Compare with the column with 81000+-51, which is correctly aligned but not rounded correctly.)
2. It does not work outside the S column definition. (See second table. My code is bad.)

It currently also only works for integers. (Doing the same for floats is certainly much more complicated -- and I don't need it right now.)

With version 3 of siunitx you can use round-mode = uncertainty, for example

documentclass{article}
usepackage{booktabs}
usepackage{siunitx}
begin{document}
  sisetup{uncertainty-mode = separate, round-mode = uncertainty}
  begin{tabular}{
    l
    S[table-format=3.2(2)]
    S[table-format=3.3(2)]
  }
  toprule
    2 tight $tau$s     & 72.293(269)     &    80.839(51) 
    2 medium $tau$s    & 212.383(461)    &   231.155(125) 
  bottomrule
  end{tabular}
end{document}

or

documentclass{article}
usepackage{booktabs}
usepackage{siunitx}
begin{document}
  sisetup{uncertainty-mode = separate, round-mode = uncertainty}
  begin{tabular}{
    l
    S[table-format=6(2)]
    S[table-format=6(2)]
  }
  toprule
    2 tight $tau$s     & 72293(269)     &    80839(51) 
    2 medium $tau$s    & 212383(461)    &   231155(125) 
  bottomrule
  end{tabular}
end{document}