The following sites have a number of very good revision exercises and model exam papers that you could use while revising for your unit assessments and also the final exam. Remember to also attend the Study Support session in the department on Tuesday lunchtimes.
https://www.youtube.com/user/HEGARTYMATHS
http://maths.qahs.org.uk/home-study-2/sqa-past-papers/ (Click on Home Study, National 5 Home Study and then scroll down to find the resources)