Cambodia uses the Cambodian Riel as its official currency, but the US Dollar is widely accepted and commonly used for larger bills. The Riel comes in various denominations, including 50, 100, 500, 1000, 2000, 5000, 10000, 20000, 50000, and 100000. However, there are no coins in circulation in Cambodia. While prices in restaurants, bars, and cafes are often listed in US dollars, bargaining is also done in US dollars. It is recommended to carry small Riel notes for small change. The exchange rate between the Riel and US Dollar is typically around 4,100, although it can vary slightly. In major towns, there are ATMs that dispense US dollars, and cash is the preferred method of payment. Credit cards are generally only accepted in hotels and larger restaurants.

Tipping is not a traditional custom in Cambodia, but it can have a significant impact on the impoverished nation. While there are no strict guidelines for tipping, it is customary to tip 10% of the total bill at restaurants, and more if the service was exceptional. For tour guides, a tip of 10% of the total cost is considered adequate, while for drivers, a tip of USD $3-5 per day is appropriate. In hotels, it is customary to tip around USD $2-3 per bag for the bellman and $1 per day for the maid. Tipping at spas and massage places is optional, and you can tip any amount you like. Tipping taxi drivers is not expected, but rounding up the fare or letting them keep the change is appreciated. Tuk Tuk or motorbike drivers do not expect tips, but an extra tip can be given for exceptional service. At temples and religious sites, it is customary to leave a few thousand Riels in the contribution boxes if someone shows you around or if a monk blesses you.

It is important to note that Cambodia has a dual currency system, with both the Riel and US Dollar being used in daily transactions. Over 85% of transactions in Cambodia are carried out using US dollars. This makes it convenient for travelers who may already have US dollars on hand. However, it is still advisable to have small change in Riel as anything less than a dollar will require Riel, and there are no coins available. It is also worth mentioning that prices in restaurants, bars, and cafes are often listed in US dollars. ATMs can be found throughout major towns that dispense US dollars. However, credit cards are generally only accepted in hotels and larger restaurants.

In conclusion, while the official currency of Cambodia is the Cambodian Riel, the US Dollar is widely accepted and commonly used for larger transactions. It is important to have both currencies on hand when traveling in Cambodia and to carry small Riel notes for smaller purchases and payments. Tipping customs vary but are not traditionally practiced in Cambodia. It is advisable to follow local customs when it comes to tipping and to leave a few thousand riels at temples and religious sites if someone provides assistance or blessings.