How to deal with Autistic tantrums?

The little girl that I babysit has Autism. She'll be turning 2 next month. She does not talk, respond to her name, play with toys, or make eye contact. She spends her time running in circles screaming, arm-flapping, etc. I love her to death, but the screaming gets to me. When you turn cartoons off, she throws a complete screaming, crying, hitting, and throwing tantrum and does not stop for a good 30-45 minutes. I literally have to hold her to stop her from banging her head on things. How do you stop these tantrums, or can you? Thanks.