Little bug in standart showing of products asImage

There is a default margin of 10 px around each product which can be changed in the hikashop options of your menus/modules.
Before creating your modules/menus, you can just change that margin option in the Display tab of the configuration and your new menus and modules won't have that margin.

Then could you give a link to your page and a screenshot of the problem so that we can see what you're talking about ?

That's because each product has a width of 9%. Since you have ten products per line, the total width used is 90% and the blank space is the 10% left of your width. That's because the system needs to round the calculations.
However, it's easy to fix with CSS. You just need to add the CSS below in the front end CSS file that you can edit via the Display tab in the configuration of HikaShop:
.hikashop_products {
margin-right: -100px;
}