How to arrange buttons with different text-sizes in a TableView so they are not displaced?

Question

I write a rpn calculator app for just for learning. The buttons are arranged in a table layout. The arithmetic buttons uses a bigger font size because the symbols are very small otherwise. This produced slightly displaced buttons, but they are all the same size. It works if all buttons use the same font size.

Look here for image: http://img512.imageshack.us/img512/3871/unbenanntnc.png

How can I prevent this?

Thanks!

Update: I also tried: android:layout_centerVertical but with no effect.

Latest result: http://img836.imageshack.us/i/unbenanntas.png/

Used styles:

<style name="CalcButton" parent="@android:style/TextAppearance.Medium">
    <item name="android:layout_width">53dp</item>
    <item name="android:layout_height">50dp</item>
    <item name="android:textColor">#000050</item>
    <item name="android:typeface">serif</item>
    <item name="android:textSize">14sp</item>
       <item name="android:layout_centerHorizontal">true</item>
            <item name="android:layout_centerVertical">true</item>
</style>
<style name="EnterButton" parent="@android:style/TextAppearance.Medium">
    <item name="android:layout_height">50dp</item>
    <item name="android:textColor">#000000</item>
    <item name="android:typeface">serif</item>
    <item name="android:textSize">14sp</item>
    <item name="android:layout_span">2</item>
       <item name="android:layout_centerHorizontal">true</item>
            <item name="android:layout_centerVertical">true</item>
</style>

<style name="NumberButton" parent="@android:style/TextAppearance.Medium">
    <item name="android:layout_width">53dp</item>
    <item name="android:layout_height">50dp</item>
    <item name="android:textColor">#500000</item>
    <item name="android:typeface">serif</item>
    <item name="android:textSize">20sp</item>
       <item name="android:layout_centerHorizontal">true</item>
            <item name="android:layout_centerVertical">true</item>
</style>

<style name="ArithmeticButton" parent="@android:style/TextAppearance.Medium">
    <item name="android:layout_width">53dp</item>
    <item name="android:layout_height">50dp</item>
    <item name="android:textColor">#005000</item>
    <item name="android:typeface">serif</item>
    <item name="android:textSize">20sp</item>
    <item name="android:baselineAligned">false</item>
    <item name="android:layout_centerHorizontal">true</item>
       <item name="android:layout_centerVertical">true</item>
</style>

Excerpt of main.xml:

<TableLayout android:id="@+id/TableLayout01" android:layout_width="fill_parent" android:layout_height="wrap_content"
android:layout_marginTop="10px" android:baselineAligned="false" >
<TableRow>
<Button android:id="@+id/BtEnter" style="@style/EnterButton" android:text="Enter" ></Button>
<Button android:id="@+id/BtBs" style="@style/CalcButton"  android:text="←"></Button>
<Button android:id="@+id/BtSwap" style="@style/CalcButton"  android:text="y↔x"></Button>
<Button android:id="@+id/BtRoll" style="@style/CalcButton"  android:text="R↓"></Button>
<Button android:id="@+id/BtC" style="@style/CalcButton"  android:text="Clr"></Button>
</TableRow>

</TableLayout>