Вы были достаточно близко, просто нужно было немного от обеих этих попыток вместе. Посмотрите, поможет ли приведенное ниже, я также добавил альтернативу, использующую массивы (если у вас много данных, это будет намного быстрее):
Sub RoundRanges()
Dim ws As Worksheet: Set ws = ActiveSheet 'better use something like: ActiveWorkbook.Sheets("Sheet name here")
Dim lRow As Long: lRow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row 'get last row
Dim lCol As Long: lCol = ws.Cells(2, ws.Columns.Count).End(xlToLeft).Column 'get last column
Dim R As Long, C As Long
For C = 1 To lCol 'iterate through each column
Select Case ws.Cells(2, C) 'get the text of the cell 2...
Case "Percent"
For R = 3 To lRow 'iterate through each row
ws.Cells(R, C) = WorksheetFunction.Round(ws.Cells(R, C).Value, 1) 'apply the desired calculation
Next R
Case "Dollars"
For R = 3 To lRow 'iterate through each row
ws.Cells(R, C) = WorksheetFunction.Round(ws.Cells(R, C).Value, 2) 'apply the desired calculation
Next R
End Select
Next C
'ALTERNATIVE:
'Dim arrData As Variant: arrData = ws.Range(ws.Cells(1, 1), ws.Cells(lRow, lCol))
'For R = LBound(arrData) + 2 To UBound(arrData) 'skip first 2 rows
' For C = LBound(arrData, 2) To UBound(arrData, 2)
' If arrData(2, C) = "Percent" Then
' arrData(R, C) = Round(arrData(R, C), 1)
' ElseIf arrData(2, C) = "Dollars" Then
' arrData(R, C) = Round(arrData(R, C), 2)
' End If
' Next C
'Next R
'ws.Range(ws.Cells(1, 1), ws.Cells(lRow, lCol)) = arrData
End Sub