D&D 5E (2014) Difficulty of Converting Pathfinder / 3.X Stuff?

[Zoetrope]

"Cut by a tenth" as in 100 gp goes down to 90 gp, or as in divided by 10, i.e. 100 gp results in 10 gp?

Sorry, should have been clearer - I meant divide by 10, so as you say 100gp becomes 10gp and so on, rounding up or down as desired.