I have a list of items
Your best bet is probably to pick one specific element type -- perhaps the one with bigger dimensions -- and assign the click handler to those only. If the onclick is set to both the A tag and the LI (through whatever means), the call may happen twice, unless you specifically prevent such event bubbling in your named function.
Is there a particular reason you want the same action to happen on both element types, instead of just one? (If it's something along the lines of "just a precaution," it's probably best to work out the issues instead of paving over them with more scripting.)