Bagaimana untuk Memusatkan Kontena dan Elemen Kanak-Kanak Jajar Kiri dalam Grid Responsif?

<code class="css">body {
    margin: 10px 0;
}
.outer {
    text-align: center;
}
.inner {
    font-size: 0; /* fox inline gaps */
    display: inline-block;
    text-align: left;
}
.item {
    font-size: 16px; /* reset font size */
    display: inline-block;
    margin: 5px; /* gutter */
}
.item img {
    vertical-align: top;
}
@media (max-width: 551px) { /* ((100+5+5)x5)+1 */
    .inner {
        width: 440px; /* (100+5+5)x4 */
    }
}
@media (max-width: 441px) {
    .inner {
        width: 330px;
    }
}
@media (max-width: 331px) {
    .inner {
        width: 220px;
    }
}
@media (max-width: 221px) {
    .inner {
        width: 110px;
    }
}</code>

<code class="html"><div class="outer">
    <div class="inner">
        <div class="item"><img src="//dummyimage.com/100"></div>
        <div class="item"><img src="//dummyimage.com/100"></div>
        <div class="item"><img src="//dummyimage.com/100"></div>
        <div class="item"><img src="//dummyimage.com/100"></div>
        <div class="item"><img src="//dummyimage.com/100"></div>
    </div>
</div></code>