Service calculator! (Tax and tip)
My only concern would be the hard coding of 15, 20, and 25, and the redundant code used to handle these 3 values:

Private Function GetTip() As Double
    If (Tip15.Checked) Then
        Return PriceBox.Text * 0.15
    ElseIf (Tip20.Checked) Then
        Return PriceBox.Text * 0.2
    ElseIf (Tip25.Checked) Then
        Return PriceBox.Text * 0.25
    End If
End Function


[...]

Private Sub Tip15_CheckedChanged(sender As Object, e As EventArgs) Handles Tip15.CheckedChanged
    If TotalBox.Text &lt;&gt; "" Then
        TotalBox.Text = Format(CalcTotal(), "currency")
    End If
End Sub
Private Sub Tip20_CheckedChanged(sender As Object, e As EventArgs) Handles Tip20.CheckedChanged
    If TotalBox.Text &lt;&gt; "" Then
        TotalBox.Text = Format(CalcTotal(), "currency")
    End If
End Sub
Private Sub Tip25_CheckedChanged(sender As Object, e As EventArgs) Handles Tip25.CheckedChanged
    If TotalBox.Text &lt;&gt; "" Then
        TotalBox.Text = Format(CalcTotal(), "currency")
    End If
End Sub


You might want to add more values later (18% seems to be a new popular tip value for some reason) or edit the existing values, so hardcoding isn't a great idea, design/style wise.