Aivars -
I could be wrong, but I had quite a problem recently in an accounting package which I developed, and it was with the Round function.
I think that you will find that if you perform further calculations with a previously rounded number, the calculation will be performed on the extended decimal places, not on the rounded (visable) decimal places.
If you go to the field of the rounded figure and place your cursor over the field you will notice that the extended decimals show up, if you do the same with a Fixed figure only the two decimal places will show.
I cleared up the problem by using the Fixed function and all the extra decimal problems were cleared up.
I am going to research this further to see if I am nuts or what <grin>.