How can we store in 'which data type' only two num after decimal and not roundoff the num in SQL

You are wrong about float.

The following code snippet

create table test (a1 float, a2  decimal(15,2), a3  numeric(15,2), a4 real)
insert into test values (2.7777,2.7777,2.7777,2.7777)
select * from test

produces the results

2.7777	2.78	2.78	2.7777

But if I change the definition of a2 and a3

create table test2 (a1 float, a2  decimal(15,4), a3  numeric(15,4), a4 real)
insert into test2 values (2.7777,2.7777,2.7777,2.7777)
select * from test2

gives

2.7777	2.7777	2.7777	2.7777

To get your desired result of 2.77 then you can use ROUND [^] forcing it to truncate. Compare these results from

select round(a1, 2), round(a1, 2, 1), round(a2, 2), round(a2, 2, 1), round(a3, 2), round(a3, 2, 1), round(a4, 2), round(a4, 2, 1) from test2 

which gives the results (I've added vertical bars to make it easier to see each column

2.78	2.77 |	2.7800	2.7700 | 2.7800	2.7700	| 2.78	2.77

You should really be doing the truncation in your presentation layer though.

In summary then, store your data in a column of type float, decimal (with enough digits right of the decimal point defined), numeric (comment as for decimal) or real and either truncate it in the UI or use

ROUND(yourColumnName, 2, 1)