Guys, thank you for your valuable opinions, but it is a matter of personal preference.
There is no question in my mind what to do for example with this banknote:
I want to repair tears on a left and right sides.
And that's my personal preference.
Otherwise I will loose this banknote which I had at least 30 years.
Also I've got couple of banknotes with some plastic tape.
After some time tape and glue underneath became dark brown.
I would prefer to take off this tape and use cigarette paper instead.
So, let's get back to question I asked:
Anybody knows transparent glue which can be used to repair valuable paper materials and does not change color?
I am sure people in museums working with antique books are using special glue.