The 6th product goes to the second line. What's the problem?

In the stylesheet file, search class .box-product > div and replace it with:
 

.box-product > div {
   width: 20%;
   float: left;
   text-align: center;
   margin-bottom: 20px;
}

 

 

In OC 1.5.1.3.1 is better:

.box-product > div {
        //width: 130px;
       width: 129px;
      display: inline-block;
       vertical-align: top;
      margin-right: 20px;
      margin-bottom: 20px;    
}