He bought 5*4=<<5*4=20>>20 shirts
The discount saves him 15*.2=$<<15*.2=3>>3 per shirt
So each shirt cost 15-3=$<<15-3=12>>12
So the total order cost 20*12=$<<20*12=240>>240
Tax added 240*.1=$<<240*.1=24>>24
So he paid 240+24=$<<240+24=264>>264
#### 264