https://petitbocq.com/wp-content/themes/theme-woocommerce/js/cart.js?ver=7.1.3

1window.addEventListener("DOMContentLoaded", (event) => 
2{
3   function set_listener_for_qty()
4   {
5      const inputs_qty = document.querySelectorAll(`[id^="quantity_"]`);
6
7      for (const input of inputs_qty) 
8      {
9         const step = input.getAttribute("step");
10
11         if( step != 1 )
12         {
13            input.addEventListener('keyup', (e) => 
14            {
15               if( ! Number.isInteger(e.target.valueAsNumber / step) )
16               {
17                  setTimeout( () => {
18                     e.target.value = Math.ceil(e.target.valueAsNumber / step) * step;
19                  },300 )
20               }
21            });
22         }
23      }
24   }
25   set_listener_for_qty();
26
27   jQuery( document.body ).on('updated_cart_totals', function( event ) {
28    set_listener_for_qty();
29   });
30
31});