If none of the above alternatives is possible, try the following procedure.
Step 1: Tune the open 6th string to either:
(a) The open 6th string of another guitar.
(b) A Piano
(c) Pith Pipes, which produce notes that correspond with each of the 6 open strings.
(d) A tuning fork. Most tuning forks give the note A.
Step 2: Adjust the pitch of the fifth string (A) so it is the same pitch as the fifth fret of the sixth string (an A note).
Step 3: Adjust the pitch of the fourth string (D) so it is the same pitch as the fifth fret of the fifth string (a D note).
Step 4: Adjust the pitch of the third string (G) so it is the same pitch as the fifth fret of the fourth string (a G note).
Step 5: Adjust the pitch of the second string (8) so it is the same pitch as the fourth fret of the third string (a D note).
Step 6: Adjust the pitch of the first string (E) so it is the same pitch as the fifth fret of the second string (an E note).