Paste Rows Based On Data In A Column

I've been using a macro that, among other things, will split a set of data into different sheets based on one column. For example, if I have Column A populated with numbers 1-10, each entry with a "1" in column A gets pasted into a sheet entitled "1", and so on. Some of the numbers I group together (for example, let's say I would group the 2s and 3s together).

I've been using the code below, but it seems to be very fickle. Half the time I run the macro, I get a "Run-time error 1004" and it points to the line "Sheets.Add. Name = WhtSht". Is there a different (easier) way to accomplish what I'm trying to do?

Dim rng As Range, StrtSht As String, WhtSht As String
StrtSht = ActiveSheet.Name
For Each rng In Range("A1:A" & Range("A65536").End(xlUp).Row)
WhtSht = rng.Value
If WhtSht = "21" Then WhtSht = "7"
If WhtSht = "34" Then WhtSht = "33"
If WhtSht = "36" Then WhtSht = "33"
If WhtSht = "37" Then WhtSht = "33"
If WhtSht = "56" Then WhtSht = "55"
If WhtSht = "57" Then WhtSht = "55"
If WhtSht = "76" Then WhtSht = "75"
If WhtSht = "97" Then WhtSht = "96"
If SheetExists(WhtSht) Then
Rows(rng.Row).Copy
Sheets(WhtSht).Select
Range("A" & Range("A65536").End(xlUp).Row + 1).PasteSpecial xlPasteAll
Sheets(StrtSht).Select
Else
Sheets.Add.Name = WhtSht
Sheets(StrtSht).Select
Rows(rng.Row).Copy
Sheets(WhtSht).Select
Range("A1").PasteSpecial xlPasteAll
Sheets(StrtSht).Select
End If
Next