Creation of contracts and number of decimals

Currently, contracts are handled in Lempiras HND and USD dollars, but in the case of dollars the exchange rate may vary depending on the day, my question is in the application of the budget since the rate may vary for the contracts because it is not fixed, as They manage the schemes when they are projects in lempiras and certain contracts in dollars for budget allocation.

Number of decimals: In ERP you can manage the number of decimals, in this case we decided to leave only two decimals, but in spring they told us that it is not possible to manage a specified number of decimals, our concern comes from the fact that in the case that it is not define in both systems a specific number in decimals we will have a variation.