add this in the customers tab see attachment cutemers[]

ps. do not use capital letters in the customers tab
[]
add in the property tap of each product[]
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
<entry key="Multi price">Yes</entry>
<entry key="price2">2.2</entry>
<entry key="price3">3.3</entry>
<entry key="price4">4.4</entry>
<entry key="price5">5.5</entry>
</properties>
this is the script set it in script.Event.Addline[]
import com.openbravo.pos.forms.DataLogicSales;
import com.openbravo.pos.forms.DataLogicSystem;
import com.openbravo.data.loader.Session;
import com.openbravo.format.Formats;
import java.lang.Math;
import java.util.*;
import java.text.*;
import com.openbravo.pos.ticket.ProductInfoExt;
import com.openbravo.pos.ticket.TicketLineInfo;
import com.openbravo.format.Formats;
import com.openbravo.pos.ticket.TicketProductInfo;
import java.lang.Math;
import java.util.*;
import java.text.*;
import javax.swing.JOptionPane;
// -------------------------------------------------------------------------------------------
// Multi price 1, 2 or ... Begin
if (line.getProperty("Multi price") != null){
if ((line.getProperty("Multi price").equals("Yes")) && (ticket.getCustomer()!= null) && ((ticket.getCustomer().getFax()) != null)){
value = (ticket.getCustomer().getFax());
Price = line.getProperty(value);
Double newPrice = new Double(Price);
// line.setPrice(newPrice);
line.setPriceTax(newPrice);
}
}
// Multi price 1, 2 or ... Einde
// ------------------------------------------
add this in the Ticket.Buttons[]
<event key="ticket.addline" code="script.Event.Addline"/>
This is a link with more explanation[]
https://sourceforge.net/p/unicentaopos/discussion/1126900/thread/e6d0d1d9/#bd00