=ROUND(IF(B3>=30000,B3*10%,IF(30000>B3>=25000,B3*5%,B3*7.5%)),2)
=round(IF(B3>=30000,B3*10%,IF(30000>B3>=25000,B3*5%,B3*7.5%)),2)加个小数点约束函数就可以了
