Can you provide screen print and the field type (currency,number, text, etc)

Have the checked the length and decimal places for the field to make sure it's what you want?

Do you have multi-currency enabled? It so, you could have a format in multi currency area also (see below).

Also, it looks like you are new to the developr forum, Welcome!!!

As a common practice, if your question is answered, please choose 1 best answer. 
But you can give every answer a thumb up if that answer is helpful to you. 

Thanks


Settings to a currency field for an object will be superseded by the setting in the Currency setup
 
For example: (Consider the Decimal Place setting on the currency field is set to 2) If you type the opportunity amount as “123.89” on the record and its Currency field Decimal Place setting is set to “0”, the amount will display as “124”. 
Similarly, if you type the opportunity amount as “124” on the record and its Currency field Decimal Place setting is set to “2”, the amount will display as “124.00”, irrespective of what the Decimal Place setting is defined at the field level.
Locating or Editing 'Decimal Place' Settings at the Currency LevelClick on your Name||Setup|| Administration Setup|| Company Profile|| Manage Currencies (If you have “Enable Improved Setup User Interface” disabled) ​OR
Click on your Name||Setup|| Administer|| Company Profile|| Manage Currencies (If you have “Enable Improved Setup User Interface” enabled)
Click on the button ‘Manage Currencies’ which will take you to the Currency Setup Page.
Under ‘Active Currencies’ section, you can review the ‘Decimal Places’ defined for individual Currency.
To make changes to the same, click on ‘Edit’ next to the Currency you want to make changes in.