I'm not entirely sure which character specifically said this line in the movie. It could be one of the many minor characters involved in the various criminal underworld dealings shown in 'Pulp Fiction'.
Honestly, I can't remember which character said it. 'Pulp Fiction' is filled with a lot of dialogue and a large cast of characters. It could be someone from the group of low - life criminals that are constantly making deals and having exchanges throughout the movie. Maybe it was one of the guys in the diner scene or one of the people at the drug dealer's place. Without a more detailed search or re - viewing, it's impossible to be certain.
There are so many characters in 'Pulp Fiction' that it's hard to recall exactly who said 'I've got five on it'. It might be one of the drug - dealing characters or just some random person in the background of one of the seedy locations like the bar or the drug den. Since the movie has a complex web of characters and their interactions, it's difficult to pinpoint without re - watching the movie with this specific line in mind.