Probability of Failure

I have been tasked to look at failure probabilities for a cash machine. For each transaction, there will be a chance of 4 distinct outcomes (with their expected probabilities):

1. Successful Transaction (95%)
2. Software Recoverable Fault (3%)
3. Unskilled Recoverable Fault (1.5%)
4. Skilled Recoverable Fault (0.5%)

During testing, there are continuous transactions being performed and the outcome of each recorded.

What would be the best method of confirming that the cash machine is indeed meeting these probabilities? Chi Square?