<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> 

<xs:element name="cost">
    <xs:complexType>
        <xs:choice maxOccurs="unbounded">
            <xs:element name="USD" type="xs:decimal" />
            <xs:element name="EUR" type="xs:decimal" />
            <xs:element name="GBP" type="xs:decimal" />
        </xs:choice>
        <xs:assert test="if (USD and EUR) then 
                             number(EUR) eq (floor(USD * (0.702644 * 100)) div 100)
                         else true()" />
        <xs:assert test="if (USD and GBP) then
                             number(GBP) eq (floor(USD * (0.620670 * 100)) div 100)
                         else true()" />
    </xs:complexType>
</xs:element>
</xs:schema>