Job Title Dilemma: Should I List My Actual Role or Official Designation on My Resume?

In my current organization, my designation is Technical Project Manager. Since the time I joined the company, I have played the role of a lead developer but never as a Technical Project Manager. If I update my resume, what should I mention as my designation? Can I mention the role I am currently playing?

Hi,

Please mention the designation that will suit your career goal in the long term.

Thank you.

If I mention being a technical project manager, how will that help me when I have never worked as a technical project manager?