It is customary to tip your dog groomer during the holiday season, but the amount depends on your individual circumstances. Generally, a 10-20% tip is appropriate, but if you have a particularly large dog or a challenging coat, a higher tip may be warranted. Additionally, if the groomer has gone above and beyond their regular duties, such as providing special accommodations or additional services, a larger tip would be appropriate. Ultimately, the amount is up to you, but showing your appreciation for their hard work is always appreciated.