Eye Exercises can help with the astigmatism but the exercises of the eyes cannot actually fully cure the astigmatism but the exercising of your eyes can help with improving your vision.
When you do eye exercises when you have astigmatism the exercises of your eyes help to improve the condition of your rectus muscles which helps to relax them and reduce their stress.
To fully cure astigmatism you will need to have Laser or Lasik Eye Surgery which vastly improves your vision and gets rid of the Astigmatism once and for all.
Not everyone can have Laser Eye Surgery or Lasik Eye Surgery but if you can and can afford to have the Lasik Eye Surgery done then it will greatly improve your vision.
My sister had astigmatism and eventually got Lasik Eye Surgery when she could afford to and it cured her astigmatism and she sees much better now.