When does my turn end?

[mickp99]

When my turn ends is an important question for Munchkin Zombies (with Voodoo Mojo).

I've found a couple of posts on the topic, but the implied answers don't seem consistent with the rules.

So... when does my turn end? Is it:
when I say so? (I can't see that anywhere in the rules).

Immediately after I discard cards for charity? This is perhaps implied by rules, but the rules also suggest that there is no charity if you have five cards or less, so when does your turn end if you only have five cards?