Hourly data

Hi All

Would appreciate if i could get help on this subject. In the file below i have data every 5 mins. However, I wish to separate the data such that i have hourly data, i.e. take out every row whose time ends with a 00, like 7:00 and 8:00 etc. As it is in the format of time, i can't retain just the last 2 digits and separate from there...could anyone help please?