Code:
$ awk -F, '{$3=sprintf("%.2f",$3)}1' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}' OFS="," testfile
$ awk -F, '{$3=sprintf("%.2f",$3)}1' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}2' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}3' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}4' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}23123412341234' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL
$ awk -F, '{$3=sprintf("%.2f",$3)}23123412341234.2345' OFS="," testfile
1400030846,2,17.00,POL GENERAL
1400030900,3,14.95,FIC GENERAL