Originally Posted by Japan Ryokan Association

...some guests offer kokoro-zuke when staying at a ryokan. When doing so, the guests usually wrap the money or place it in a small envelope called a pochi-bukero and hand it as a shougi (generous tip), sunshi (small token of appreciation), or chadai (small tip) usually given to the room attendant. The kokoro-zuke is given at various timings, such as upon arrival, at dinnertime, or upon departure. The amount is usually 10% of the accommodation charge, but as a kokoro-zuke is at the discretion of each guest, there are no set rules. Some ryokans firmly decline gifts of kokoro-zuke.