VBA convert time to nearest 15th minute block excel

I need a function for excel vba which will convert the time to the nearest 15 minutes block. This is the scenario: I want to multiply 0.73 to 26.25 hrs(the column is formatted to "h:nn" ) to get me 19.15 hrs( if the result is 19:18 (i.e. greater than 15 minutes)(then round it to 19:30 otherwise round it back to 19:00) Please let me know if you need any further clarifications. Thanks