Insert values with leading zeros
As is suggested in the comments, you should change the data type to, for example, char(3). If that is not possible, you can transform the value of the column like:

SELECT SUBSTR(DIGITS(CURRENCY_CODE),1,3) AS CURRENCY_CODE
FROM ...


or perhaps:

SELECT DIGITS(CAST(CURRENCY_CODE AS DECIMAL(3,0))) AS CURRENCY_CODE
FROM ...


which would be the same as:

SELECT DIGITS(DECIMAL(CURRENCY_CODE, 3,0)) AS CURRENCY_CODE
FROM ...


when you retrieve it