If you simply want to show your time in this format, you could put this formula
=HOUR(A1)&TEXT(CEILING(MINUTE(A1),15)/150,".0")
Next to cell A1, for instance.
You could run this along side your actual times and perform all calculations using the real time.
This could may lead to different results, such as when 7 and 2 seconds are added:
Time formula
0:07 0.1
0:02 0.1
0:09 0.1 (:09 = .01, not .1 plus .1 =2)
Another caveat, :45 would have to be enter as 0:45 with this conversion formula.
sorry if I'm way off base.
Your sample data didn't include 10:23 or 8:08
so I wasn't quite sure how you wanted it handled...
=HOUR(A1)+INT(MINUTE(A1)/15)/10 ...always rounds down.
=HOUR(A1)+CEILING(MINUTE(A1),15)/150 ...always rounds up.
=HOUR(A1)+ROUND(MINUTE(A1)/150,1) ...rounds up at increments of 7.5.