In general, under federal ethics rules, a federal employee may not give, or solicit a contribution for, a gift to an official superior, and may not accept a gift from an employee receiving less pay if the employee is a subordinate.

But on occasions “where gifts are traditionally given” such as the holidays, employees may give the following to an official superior: items, other than cash, valued at $10 or less; items such as food and refreshments to be shared in the office; and personal hospitality provided at a residence which is of a type and value customarily provided by the employee to personal friends.

More background here:
https://ask.fedweek.com/federal-government-policies/rules-gifts/