PREAMBLE: I didn't understand your question at first but then I realized you can't be dealing with text values (currency symbol + digits) for this, so you need to be dealing with cells containing values formatted so that they show as currency amounts but that actually contains only numbers (simply digits, no currency symbols).
Well, since Excel still doesn't provide a sorting based upon cells formatting (besides of colors/icons) at this time, the only solution that comes to my mind is basically the second you hypothesized: you need to put a relative currency symbol for each amount (row) in a secondary column; that way you could then do a custom multi-level sorting (first-level on the currency column and second-level on the amount column) and get your data sorted out.
What I can do, now, is suggesting you a way to automate the process so to make things faster and assuming you don't want to do things like writing currency symbols for every amount row by hand (do you? ;-D).
OK, so if you can use VBA for this, here we go...
1) Put the following VBA code in a module:
Public Function GetCurrency(ByVal r As Range) As String Application.Volatile Static RegX As Object If RegX Is Nothing Then Set RegX = CreateObject("VBScript.RegExp") With RegX .Global = True .Pattern = "[0-9\-\.,\s]" GetCurrency = .Replace(r.Text, "") End With End Function 2) Now, assuming amounts values are in column "A" and currency symbols shall be on column "B", put this formula in the first column B row (B1 cell):
=GetCurrency(A1) then copy that formula down for all the needed subsequent rows of the same column (B).
OK so, by now, you got the two columns, the one with formatted amount values (A) the other one you needed containing the relative currency symbols (B).
PLEASE NOTE THIS WILL WORK ONLY IF MY PREAMBLE ASSUMPTIONS ARE MET AND THEREFORE YOU HAD COLUMN "A" CONTAINING NUMERIC VALUES FORMATTED AS PROPER CURRENCIES. IF NOT, HAVING TO MANUALLY FORMAT EACH COLUMN "A" ROW/CELL AT THIS POINT MAKES NO DIFFERENCE AND NO BENEFIT/GAIN OVER THAN DIRECTLY WRITING CURRENCY SYMBOL BY HAND ON EACH COLUMN "B" ROW/CELL
3) Now select the two columns and do the custom multi-level sort:
Go to "Data" ribbon, look for "Sort & Filter" group, click "Sort";
Sort COLUMN B VALUES (first level)
Click on "Add Level"
Sort COLUMN A VALUES (second level)
and... you're done!
P.S.: Now, if you wish, you can even safely hide the "B" column.
REFS: More on multi-column based sorting.
IMPORTANT FINAL NOTE:
you don't have to manipulate/modify in no way the values in the amounts column, currency symbols NEED TO BE in a secondary column for this. You can't just add currency symbols to your amount values column 'cause, otherwise, you'll get amount as text values and therefore won't be able to sort them properly as numeric values would! (Think, for example, about what happens when you have "$80", "$30", "$500" as text values: "$500" will be sorted between "$80" and "$30" because as chars: "8" < "5" < "3" ...Hope you got it.)