Centering column values in a table that's already centered?

I am working with the following code for a table :

begin{table}[!h]
    centering
    begin{tabular}{@{} lllll }
    toprule
     textbf{mytab{DM}}
      & multicolumn{3}{c|}{textbf{mytab{Epistemic $>$ Root}}} &  multicolumn{1}{c}{textbf{mytab{Root $>$ Epistemic}}}
      midrule
       & textbf{mytab{E--E}} & textbf{mytab{E--R}} & textbf{mytab{R--R}} &  textbf{mytab{R--E}} 
      midrule 
      textit{mytab{Must Used to (...) Will Ought to}} & .27 & .25 & .23 & .22
      bottomrule
    end{tabular}
    caption{Proportions of semantic ordering of DMs with 5 tokens or less, from textit{Must Used to} to textit{Will Ought to} (n=59)}
    label{tab:low_freq_DM_semantics}
end{table}
FloatBarrier

As can be seen in the output, the values in the second column (Root > Epistemic) are left-aligned and I would like to center them within that large column to make them stand out from the values in the first. I have tried using centering inside the column but also manual commands like hskip, qquad, but nothing happens when I do this. Would appreciate some help as I sometimes struggle wrapping my head around Latex tables, although I expect the solution to this problem is pretty simple!

All the best,

Cameron

documentclass{article}
usepackage{booktabs,siunitx}

begin{document}

begin{table}[!htp]
centering

begin{tabular}{
  @{}
  l
  *{4}{S[table-format=1.2]}
  @{}
}
toprule
textbf{DM} &
  multicolumn{3}{c}{textbf{Epistemic $>$ Root}} &
  {textbf{Root $>$ Epistemic}}
cmidrule(r){2-4} cmidrule(l){5-5}
& {textbf{E--E}} & {makebox[6em]{textbf{E--R}}} & {textbf{R--R}} &  {textbf{R--E}} 
midrule 
textit{Might Can}   & .27 & .25 & .23 & .22 
textit{Might Could} & .34 & .66 & 0   & 0   
textit{Can Could}   & .24 & 0   & .75 & 0   
bottomrule
end{tabular}

caption{Proportions of semantic ordering of DMs with 5 tokens or less, 
  from textit{Must Used to} to textit{Will Ought to} ($n=59$)}
label{tab:low_freq_DM_semantics}

end{table}

end{document}

documentclass[varwidth, border=3.141592]{standalone}
usepackage{booktabs, makecell, multirow}
renewcommandtheadfont{bfseries}
renewcommandtheadgape{}
NewExpandableDocumentCommandmcc{O{1}m}{multicolumn{#1}{c}{#2}}
usepackage{siunitx}

begin{document}
    begin{table}[!h]
    centering
begin{tabular}{@{} >{itshape}l SSSS }
    toprule
thead{DM}
    & mcc[3]{textbf{Epistemic $>$ Root}}
            &  mcc{thead{Root $>$ Epistemic}}                     
      cmidrule(r){2-4}cmidrule(l){5-5}
    &{thead{E--E}} &{thead{E--R}} &{thead{R--R}} &{thead{R--E}}
      midrule
makecell[l]{Must Used to (...)
          Will Ought to   }
    & .27           & .25           & .23           & .22
      bottomrule
    end{tabular}
caption{Proportions of semantic ordering of DMs with 5 tokens or less, from textit{Must Used to} to textit{Will Ought to} (n=59)}
label{tab:low_freq_DM_semantics}
    end{table}
end{document}