Try wrapping the cell value into a div with a fixed height using the formatter / cellFormatter function inside your grids layout specification. A formatter function can transform your cell value from "This is the my cell value."
to
"<div>This is the my cell value.</div>"
.
Check this out:
http://dojotoolkit.org/reference-guide/1.6/dojox/grid/EnhancedGrid/plugins/CellFormatter.html