Explanation:

- Errors of commission involve mistakes in recording, posting, or balancing financial transactions.

- Option 1: Overcasting of sales book - This is an arithmetic error in addition or totaling, typically considered an error of commission.

- Option 2: Credit sales to Ramesh Rs 5,000 credited to his account - Incorrectly crediting instead of debiting is an error of commission.

- Option 3: Wrong balancing of machinery account - Incorrect balancing is also considered an error of commission.

- Option 4: Cash sales not recorded in cash book - This is an error of omission, as the transaction was completely missed, not recorded incorrectly as in errors of commission.