There is no obligation to leave a tip in Sweden, and gratuity for service charges like hotel staff or hairdressers is already included in your total bill. Tipping is not expected for these type of services in Sweden - with two exceptions:
Swedish tipping behavior changes when you go out to eat or drink. It's common to leave a small tip of 5-10% in a restaurant or bar. In Sweden, you tip by rounding up the amount of the bill.
For example, if bill for your dinner is 121.60 it would be appropriate to give the waiter an even amount of 130.- in Swedish kronor, the local currency.
Note that you can also give taxi drivers a tip that is a little higher. Also give this tip in form of "rounding up" to the nearest even amount (e.g. for a charge of 73.50, simply give 80.00 even).