Those changes can be made by modifying your receipt XML Package. By default, the cart uses "notification.receipt.xml.config". To be sure what XML Package you are using, check the value of your "XmlPackage.OrderReceipt" AppConfig.
Here are general guidelines, on how you would proceed to make the changes to a stock receipt XML Package:
1) Search for the following:
Code:
<!-- Ext Price Column -->
<td width="20%" style="font-weight:bold; text-align:right; padding-right:1em">
<xsl:value-of select="receipt:FormatCurrencyWithoutCurrencyCode(DisplayExtPrice)" disable-output-escaping="yes" />
<xsl:if test="$applyVat = true()">
<div style="font-weight:normal">
<xsl:value-of select="receipt:FormatCurrencyWithoutCurrencyCode(ExtVatAmount)" disable-output-escaping="yes" />
</div>
</xsl:if>
</td>
The code within the td tag, is responsible for displaying the sale price of each respective item on your receipt.
2) Scroll up until you find the following:
Code:
<!-- Price Column -->
This is where your regular price is being displayed, and where you will want to insert the sale price code, with some alterations. You will essentially want to insert logic that will only insert a sale price, if it exists. Otherwise, it should return the regular price.
3) Since you will be displaying the sale price + regular price in a single column, you may need to alter or remove some other columns. If so, you will also want to look at the GenerateLineItemHeaders template - which is responsible for column headers. Remember to keep track of your rows + columns, or the table on your receipt may not generate as you expected.
Let us know if you have any questions.
Robert