Major hotels:  All hotels services inclusive of 21% tax. 11% is government tax and another 11% is service charge. Therefore, tipping is not mandatory. However, if you want to tip, give 5-10% of the total bill. 

Restaurants: some restaurants will include 5-10% service charge to their bill. But if they don't levy any service charge, you can tip between Rp5,000 to 10% of the total bill.  

Taxi drivers: tipping is not mandatory. Although all taxis are metered, some drivers did not carry coin. So it is wise to round up your bill. E.g. Your taxi meter shows Rp17,750. You can pay Rp18,000 or if you find the service is terrific, giving Rp20,000 is ok. 

Car-hire drivers:  It is not mandatory; however if service is satisfactory a basic RP 1,000 tip is deemed appropriate. (Car-hire drivers generally expect a larger tip.)

Airport porters:  For a small bag, expect to pay RP 2,000; for larger bags, expect to pay RP 3,000.

If tipping is not in your culture, then you really don't have to tip at the restaurants, hotels, taxis, etc in Bali. This also applies to those on a budget. While the Balinese (and anyone else for that matter) would greatly welcome tips, it's OK even if you don't tip them. Having said that, it's also fine if you run short of cash and don't tip or if you forget to bring cash for attendants.

Update Jan 07:

Most hotels and some restaurants charge about 21% on top of the bill -  10% Government Tax is added on, and then 10% service charge added to it.   Check your bill for this, and if it has been added, no further tip is required (unless you want to).

Airport porters expect about 5000rp per bag.   You don't have to use them, but for very little money they can be  a big help especially going through customs and it makes a difference to them.