Can't align headings on Advanced Grid

Hello, I might just be missing something obvious but I am trying to change the alignment of the headers on an Advanced grid. The version of Thingworx I am using is 8.5.3 and I was able to change the text alignment of the data with this custom css:
.myAdvancedGridClass .objbox table tbody tr td{
text-align: center !important;
}

but I also want to change the alignment of the headings to match. Any help or insight is greatly appreciated. I was looking at the documentation for Thingworx 8 and I saw that header and cell text alignment is a feature so I might just not be seeing where I can change that.