Many daily expiries get attention, but weekly and monthly ones carry weight too. Large open interest at a strike on a Friday can influence price throughout the week as dealers hedge.
The effect is hardest to measure. Gamma hedging means that dealers who have sold options buy as price falls toward a strike and sell as it rises, which dampens movement near the strike. Away from it, hedging can amplify moves.
A scalper who sees heavy interest at a nearby strike might expect range behaviour around it, and a stronger move once price moves away. It's a nuance, not a rule.
Bank research notes and some data sites publish expiry lists. They're approximate, but they give a rough map. Marking the biggest strikes on the chart each morning takes a moment.
After a month, the notes will show whether those levels behaved differently from ordinary round numbers. Either answer is useful.
Which expiry sources are trusted, and are strikes tracked against what price did?