Try this


select decode(trunc_date,round_date,trunc(sysdate)+1/24/60/60,round(sysdate)+1/24/60/60) new_date
FROM
(
select to_char(round(sysdate),'dd-mon-yyyy hh24:mi:ss') round_date,
to_char(trunc(sysdate),'dd-mon-yyyy hh24:mi:ss') trunc_date
from dual
)