After rounding the amount for trip payout, close rounding differences. To simplify this use
automatic closing of rounding differences.
Making trip payment you rounded up the amount.

The document is not entered in the field due to existing rounding difference.
After posting trip and cash disbursement which was used for payout, close roundng differences. If you make payments for trips in this way (by rdounding then), it is best to do this on a monthly basis.
Below you can see posting lines:

Enter all the criteria in the Rounding Differences window. Clicking the Close button transfers all lines which meet the entered criteria in the bottom section.

Mark the lines and click the Post button. The selected lines get posted and a journal entry is created.

Returning to Browse Posts you see the following:

This way we closed the rounding differences that were created in trip.