By anything other than Scandinavian standards, Denmark is certainly an expensive country. Post offices will change foreign cash and they are open on Saturday mornings which can be handy.
Most major banks have ATMs which give cash advances on credit cards.
There are also 24-hour cash exchange machines in Copenhagen. Restaurant bills and taxi fares include service charges in the quoted prices. Further tipping is unnecessary, although rounding up the bill is not uncommon when the service has been good. Bargaining is not a common practice in Denmark. We encourage you to verify any critical information with the relevant authorities before you travel.