Round numbers attract orders: stops, limit entries, options strikes. That makes them relevant for scalpers.
For traders who want to focus on one level type, the previous day's levels are a good starting point because they are objective: everyone sees the same high and low, apart from the server time differences discussed elsewhere on the forum.
Observed behaviour:
Price often hesitates or reacts around .00 levels.
Stops clustered just beyond round numbers can create fast moves when triggered.
Large option expiries at round strikes can pin price near them before the 10:00 New York cut.
How scalpers use them:
Avoid entries right in front of a round number in the direction of the trade.
Look for reactions, not exact touches.
Place stops a few pips away from obvious round-number levels.
Do you include round numbers in your levels, and do you see a difference between .00 and .50?
I mark .00 levels on majors and treat .50 as optional noise unless options open interest is clustered there. On EURUSD the big figure has stopped me from chasing more times than it has given me an entry.
Stops parked a few pips beyond the round number get hunted often enough that I now place them either well clear or on structure that is not the round itself. A stop at 1.1002 after buying above 1.1000 felt clever until it became the liquidity pool.
Option expiry pin into the 10:00 New York cut is real on the days I bother to check open interest. Those sessions I fade less aggressively into the figure because price can sit there longer than a normal scalp wants.
Previous day high or low that also lands on a round number is the combination I respect most. Alone, either level is weaker.
Do you see a cleaner reaction on .00 than .50 on JPY pairs as well, or does the wider pip make that distinction less useful? On USDJPY I still care about the big figure more than the half.
