from decimal import Decimal, ROUND_HALF_UP
cent = Decimal("0.01")
gross = 3 * Decimal("12.50") + 2 * Decimal("8.00")
goods = (gross * Decimal("0.90")).quantize(cent, rounding=ROUND_HALF_UP)
shipping = Decimal("5.00") if goods < Decimal("50.00") else Decimal("0.00")
tax = (goods * Decimal("0.08")).quantize(cent, rounding=ROUND_HALF_UP)
total = goods + shipping + tax
assert gross - goods == Decimal("5.35")
result = {"gross": str(gross), "discounted_goods": str(goods), "shipping": str(shipping),
          "tax": str(tax), "total": str(total)}
import json
print(json.dumps(result, ensure_ascii=False, sort_keys=True))