You are almost using MVVM, but where is your ViewModel? With a ViewModel this becomes easy.
You have an Model object you are using for your DataSource: AccountJobList
It is a list of Model objects, which I assume is AccountJob.
So perhaps AccountJob doesn't have an IsChecked property or it does but it doesn't implement INotifyPropertyChanged. That is why we create ViewModels.
So create an AccountJobViewModel that is a wrapper to AccountJob. This AccountJobViewModel must implement INotifyPropertyChanged. Now in our ViewModel we add an IsChecked property.
Now we create an AccountJobListViewModel that inherits ObservableCollection (or List<AccountJobViewModel>
if you don't need your collection to be Observable). AccountJobListViewModel takes in an AccountJobList and foreach AccountJob in the list, it creates an AccountJobViewModel and adds it to the collection.
You also need a property for SelectedItems in either the AccountJobListViewModel or its parent. I assume your Select/Deselect methods are in a ViewModel of some sort, so perhaps it goes there.
Now you simply bind IsChecked on your ViewModel.
<CheckBox IsChecked="{Binding IsChecked}" />
Now in your code, you simply set each selected AccountJobViewModel's IsChecked property to true.
private void Select(object selectedObjects)
{
foreach (AccountJobViewModel item in SelectedItems)
item.IsChecked = true;
}