What this game trains
Speed Cashier works with retail-sized prices rather than large totals — mostly one and two digit dollar amounts with cents at the lower difficulties, climbing into the low hundreds higher up. Short values arriving one after another put the emphasis on turnaround time between entries rather than on handling any single long number.
Tips for improving
The measurable gain in this game is almost always in the gap between pressing Enter and starting the next entry. Keep your hand planted; do not reset your position between rounds.
Cents endings repeat a lot in price data — 99, 95, 49. Learning those three as single finger patterns rather than two separate strokes will shave real time off a session.