Running Average for Last 5 Days

EXL Service Philippines analysts need a daily sales metric for an operations reporting dashboard. Write a PostgreSQL query that calculates the running average of sales for the current day and the four preceding calendar days.

Requirements

1. Return every date in reporting_calendar, including dates with no transactions.
2. Calculate daily_amount, treating missing transaction days as zero and ignoring NULL transaction amounts.
3. Calculate five_day_running_avg using the current date and up to four preceding calendar dates.
4. Round the running average to two decimal places and sort the output chronologically.

The window covers the current date and the 4 calendar days before it; a date that is not in reporting_calendar is simply absent from the window (the average is over the calendar dates present).