Street stalls price in round figures far more consistently than restaurants do. The reason is that the price is chosen to speed up the transaction rather than to sit at the exact point demand would support.
The queue is the constraint
A stall's income is limited by how many people it can serve in a rush, and every second spent handling money is a second not spent cooking or handing over food.
Counting out small change turns a two-second exchange into a ten-second one, and across a lunch rush that difference costs a meaningful number of customers.
Round pricing removes the counting entirely, so the money moves as fast as the food does.
Cash physically limits what is practical
A vendor working from an apron pocket can hold only a few denominations, and running out of a particular coin stops the line completely.
Prices that generate change in one or two common denominations keep the float manageable and reduce trips to break notes.
This is why prices tend to cluster at the same intervals across an entire market, since the vendors are all managing the same coinage.
Price changes come in steps, not increments
When costs rise, a stall cannot easily add a fraction to the price without breaking the arrangement that keeps the queue moving.
Instead the price holds until pressure accumulates and then jumps to the next round figure, which is a larger increase applied less often.
Between those jumps the portion is the adjustable variable, which is why quantities quietly shrink or grow while the number on the board stays still.
Round prices are easier to remember and compare
A customer walking past several stalls makes a decision in seconds, and a simple price is processed faster than an awkward one.
It also makes the mental arithmetic of ordering for several people trivial, which matters where groups buy together.
Vendors who price awkwardly find themselves explaining the total, which slows exactly the interaction they need to be quick.
Card payment is changing the logic slowly
Where card and phone payment dominate, the reasons for round pricing weaken, since no change is counted and no float is required.
Terminals introduce their own delay while a payment authorises, and fees take a share of every small transaction, which pushes vendors toward minimum order values instead.
The round numbers persist anyway in many markets, partly from habit and partly because they still do the work of making a price legible from a distance.