If you really want the data to be displayed literally the way it is in the source file, you have to deal with trade-offs. The simplest way is to format the data as text. You can do this a cell at a time or for entire columns:
loWorksheet.Columns["A:E"].NumberFormat = "@";
The trade-off is it's just text at this point. You can't add, sum, average, whatever.
On the other hands, if your data looks like this:
4.0
4.00
4.000
You can't really keep it as numbers and expect to retain the original format without doing some funny business.
If it's consistently two decimal places, and you know it's going to be, then I agree with @RenatZamaletdinov's solution.
And you might want to consider other strings and what Excel might to do them
0000123 becomes 123
10/23 will probably render as a date, depending on your localization
12345678901234567890 will render as scientific notation probably
These are all avoided if you make the numeric format text (@
), but again without knowing what you plan to do with the data, it's hard to say if this is the correct approach.