I have 2 ways of closing the circle:
#1
Draw a banishing pentagram while standing in the center of the circle. Say
Guardians of the East, South, west, and North. Powers of Earth, Air,Fire and Water I thank you for joining in my circle and I ask for your blessings as you depart. May peace be between us now and forever. Blessed Be!
#2
Once the rite is ending, face North, hold the wand up and say:
Farewell, Spirit of the North. I give thanks for your presance here. Go in power and love.
Repeat this at each point. When done, take your athame and go to the North. Pierce the energy field of the circle and bring the power into the athame. When you return to the North, the circle is no more.
Yes, it is important to close the circle properly. The energy you raise during the ritual is trapped in this circle. When you release the circle, the energy is released into the universe. Never leave a circle un opened.