Only if you never use your battery! ;D A 5 watt panel is a trickle charger at best, and may maintain the charge on a fully charged battery, but it would take forever to recharge one that's been drained even partially; like 20-30%. And that's only if you have full sun. Others here use solar, and can provide more detail on what you may need based on your intended usage.
Do you just want a panel to charge the battery while the RV is in storage or do you want to rely mostly on solar power for your camping needs? These are two different questions with vastly different answers.
See the article at http://www.rvforum.net/index.php?option=com_content&task=view&id=175&Itemid=63 for a discussion of using a solar panel for battery charging. To size the solar system for extended boondocking use, you need to calcuate your daily power requrements, this determines the battery capacity you need and the amount of solar panel capacity you will need. Serious solar users will have 200+ watts of solar panels and still require some generator usage to keep the batteries charged when the sun isn't shining. Solar is expensive.