The comma before the AND is called the Oxford comma or serial comma. Some people use it, some don't; it's a style issue really.
There are special cases, like the "tea, toast, and peanut butter and jam" case, where the meaning is confused if you use a comma before the last AND.
"I had tea and cake, cheese and crackers[,] and toast and jam"
The comma in brackets is the serial comma.
The other ANDs are not part of the "a, b[,] and c" structure, so they don't have a comma before them (and using one would look totally wrong).
In this case, where there are lots of ANDs in the sentence, the serial comma gives it a rhythm that emphasises the intended meaning, so I would always use it in those cases.
"I had tea, cake[,] and toast"
In this simple case, the serial comma adds a pause before the AND, which doesn't seem to clarify the meaning, so I omit it for brevity, but ultimately it is a style issue.