It's very reasonable to expect a 5 yr. old to be responsible for keeping their room clean and toys picked up. It's unreasonable to expect them to do deep cleaning on a regular basis, but it is appropriate for them to keep their things clean and tidy, put their dished in the sink when they are finished, and put away things they use. This is a great opportunity to teach them respect for their belongings and their surroundings.
The key to helping them keep things clean is to clearly state the exact tasks you expect them to complete. For example, instead of using a vague statement such as "keep your room clean," give specific examples of what they need to do such as "all of your clothing needs to be hung in the closet or folded in drawers, and your toys need to be placed in storage containers, not lying on the floor."
Sit down with your child and write a list together of specific chores they need to complete, then keep a copy of that list on the refrigerator and in their room so they can be reminded of what is expected. Also, after the list is completed, physically practice showing them what you want done for each of the items on the list you created. Often a kids idea of what it means to clean something is very different from a parents:)
Remember that it's very important for you and your husband to be in agreement on your child's responsibilities. Take time for both of you to be able to discuss your opinions as to what is appropriate, but ultimately you need to come to a unified decision on what is to be expected of them. Be sure to give lots of positive praise when your 5 year old follows instructions. They are more likely to keep things clean when noticed and praised for it.
I am going to cast my vote on "clean and organized." If not at age five, then when? Would I allow my five-year-old to have a messy room and then change that at six? I think the habits of picking up after yourself are good ones to establish at an early age.
It's a lot easier to say these things now that all of my kids are are past that age, but it seems to make sense to write down the standards and keep the list handy.
I will put my dirty clothes in the laundry basket.
I will put clean clothes on hooks or in drawers.
I will put toys away when not playing with them.
I will keep my room clean even if I didn't make it messy.
The value of the list, especially if unobtrusively taped to the back of the door, is that you can silently point to it when needed and potentially circumvent the escalating verbal barrage that often starts with "Clean up your Room!"
There are reasonable limits, of course. I wouldn't have my child wiping down walls with Lysol or Clorox, for example, or vacuuming (yet). But I have had my kids use a Mr. Clean Magic Sponge on their door frames and the wall around the staircase railing a few times.