Try this solution:
create table #temp
(
transaction_amount decimal(5,2),
Card_No nvarchar(50),
transaction_date dateTime
)
Insert Into #temp values(100.23,'123', '2014-02-03 12:22:36.140'),
(120.23,'123', '2014-02-02 12:22:36.140'),
(140.23,'123', '2014-02-03 12:25:36.140')
SELECT SUM(transaction_amount) as SUM from #temp where Card_No ='123'
AND convert(varchar(12), transaction_date, 105) = convert(varchar(12), getdate(), 105)
drop table #temp