How to round up time variable to nearest half-hour periods?

[hussainkw97]

I have a time variable and I want to round the observations to the nearest 30 min. 

so 2:15:00 for example would be 2:30 

5:05:00 would be 5:00:00

5:20:00 would be 5:30:00  and so on. I would appreciate any help. 

I'm using base SAS 9.4

[PeterClemmensen]

data have;
t='5:05:00't;output;
t='5:20:00't;output;
format t time.;
run;

data want;
   set have;
   roundedtime=round(t,'00:30:00't);
   format roundedtime time.;
run;