Yes. Actually, the charging slows down when it hits 80% and stops completely when fully charged. You can not hurt the battery.
Additional information below.
Use Your iPad Regularly
For proper reporting of the battery’s state of charge, be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).
Elsewhere, Apple elaborates and explains that two half-discharges (or four quarter-discharges, etc.) equals one full discharge.