fix: Included tax calculation

[iamareebjamal]

Previously, tax was being calculated using wrong formula (same as excluded). Now, it uses correct formula for included tax

[codecov]

Codecov Report

Merging #7037 into development will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           development    #7037   +/-   ##
============================================
  Coverage        60.59%   60.60%           
============================================
  Files              260      260           
  Lines            12885    12886    +1     
============================================
+ Hits              7808     7809    +1     
  Misses            5077     5077           

Impacted Files	Coverage Δ
app/api/helpers/order.py	66.12% <100.00%> (+0.27%)	⬆️

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