Tax exclusive if coupon applied else tax inclusive in items - php

Question

I have setup taxes inclusive for all my items and filled MRP in price. But now I want to apply tax inclusive if customer didn't applied coupon i.e. buying on MRP. But when customer applies coupon I need to apply taxes on after discount amount.
Is it possible with settings within Woocommerce or is there any plugin available?
For e.g.
**Case I**
Product MRP = 670
Shipping = 50
Tax 18% = 102
Final price = 670 (Including Taxes)
It's Fine.
**Case II**
Product MRP = 670
Discount 40%= 268
Price = 402
Shipping = 50
Tax 18% = 61
Final price = 452 (Including Taxes)
But I need tax to calculated exclusively on discounted price i.e. 402+18% = 474+50 (Ship) = 524
I have tried following filter in my custom plugin:
add_filter( 'woocommerce_calc_tax', 'inc_or_exc',10,3 );
// add_filter( 'woocommerce_calculate_totals', 'calculate_totals',11 );
function inc_or_exc( $taxes,$price,$rates ) {
// echo "<pre>";
if(!empty(WC()->cart->coupon_discount_amounts)){
return WC_Tax::calc_exclusive_tax( $price, $rates );
}else{
return WC_Tax::calc_inclusive_tax( $price, $rates );
}
}
But it calculates taxes bit strange. If item MRP is 100, it shows 98.85 and also totals are not updating with new taxes and shipping rates after plugin run. If I disable plugin then item MRP is shown fine i.e. 100.

Answer 1

Finally I have solved it.
First I applied inclusive exlusive filter. Then called woocommerce_calculated_total with custom condition and achieved my motive.
add_filter( 'woocommerce_calc_tax', 'inc_or_exc',10,3 );
// do_action('add_points');
add_filter( 'woocommerce_calculated_total', 'custom_calculated_total', 10, 2 );
function inc_or_exc( $taxes,$price,$rates ) {
// echo "<pre>";
if(!empty(WC()->cart->coupon_discount_amounts)){
return WC_Tax::calc_exclusive_tax( $price, $rates );
}else{
return WC_Tax::calc_inclusive_tax( $price, $rates );
}
}
function custom_calculated_total( $total, $cart ){
// echo "<pre>";
if(!empty(WC()->cart->coupon_discount_amounts)){
return round( $total + WC()->cart->get_cart_contents_tax(), $cart->dp );
}else{
return round( $total, $cart->dp );
}
}