using a function

This problem is driving me crazy - please help.

The problem in a nutshell is as follows:

Sub Macro2()
Dim xxx As Double
xxx = 0.05
Call NewFuntio(xxx)
End Sub

Sub NewFuntio(temp)
Dim t1,t2 As Double
t1 = (temp + 1) ^ (1 / 12)
t2 = 1.05^(1/12)
End Sub

t1 = 1.00407412390531
t2 = 1.00407412378365

t1 is the wrong answer and t2 is the correct answer.

Why is the function giving the wrong answer?

Thanks