the below chart shows 5-13 band and 5-21 close ema (blue-red)
you will notice 2 things
1. that in a trend the 5-21 is to one edge of the 5-13 band.........so in a DT the trend SL is above the high of band and in UT the trend SL is below the low of band
2. it generally goes sideways in the band (here for this TF it is a small zone but for higher TFs the zone is bigger before it decides to resume/reverse
so I use the bands rather than just ema of close
for bank NF I have found the 3-13 15-13 60-13 and daily-13 suitable to get info of higher TFs where the decision points of that TF are for trend changes......
for 5min you can test 5-13 itself as you have been using 5-21close successfully for swift
approximation would be 3x13 ~ 5x8.....butthe smaller the ema the more rough it is going to be.