I visit bali since 1995 at least once a year; sometimes crossing to Lombok too, mostly self-drive rental car. Several times stopped by the police, no problems at all, they never ask money, and I never once bribed the police, not a cent, for any reasons. Simple, I have never violated the rules.
Most cases is, people break the rules and then ask for help to get light fine and or the vehicle is not seized.
Ironically this conditions are contributed by the mindset that bribery is common, all police are bad and corrupt.
It is undeniable that there are bad cops, but there are also quite number of good ones. However, good cop is not attractive to discuss.