There is a way to get the look of Merge and Center without the inconvenience.
Select the cell containing the text you want centered and the adjacent cells across that you want centered. Using Ctrl+1 to access the Format Cells dialog box, click on the Alignment tab. You can also click on the dialog box launcher in lower right corner of the Alignment group on the Home tab. Click the dropdown arrow in the Horizontal field at the top and select Center Across Selection.