[FIX] pos_cash_rounding: fix "almost zero" error

TLDR: zero is not always zero in js

STEPS:

* On your POS, add a Cash rounding > Rounding precision 0.10 > Rounding method
DOWN
* Set a product with a Unit of Measure with 3 decimals (kg for instance)
* In POS:

  - Make an order for 0.514 kg at 429.99€ + 0.510 kg at 429.99 + 0.60€
  - The total of the order is 440.90 (exact total would be 440.90976)

BEFORE: The total to pay is 440.80

AFTER:  The total to pay is 440.90

WHY:

* var total = round_pr(this.get_total_with_tax(), this.pos.cash_rounding[0].rounding);

  // 440.90000000000003

* var rounding_applied = total - this.get_total_with_tax();

  // 5.684341886080802e-14

---

opw-2357917

closes odoo/odoo#60749

X-original-commit: 262a9dc935d74b30ffeaff6d6d88aac150793d6e
Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>