I'm guessing you're at a very informal type of employer, where you do what ever tasks need accomplished. In which case, I don't see any reason to expect anything above or beyond your regular wages for doing any type of job within your scheduled hours. Hell, I do stupid off-the-wall crap at my job all the time (change light bulbs, salt the walkways in winter, etc) when it's clearly not in my job description (professional office job).
Oh...and I don't tip, anybody //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif