You may come across this Salesforce validation error when deploying StandardValueSet or CustomField metadata types:

"One of the objects selected for your roll-up summary uses dated exchange rates and the other object does not. Roll-up summary fields can only summarize values of currency fields if both objects convert values or both objects do not."

The above error suggests that there is probably a roll-up summary field (in the source environment) that is using a value from LeadSource in another object.
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Finding that roll-up summary field in the source and deleting it can help with successfully validating the deployment package.

It's possible that in this scenario it is the Lead object that needs to be checked, since the error message is referencing this object's StandardValueSet.

However, if the object in question (e.g. Lead object in which the roll-up summary field may be located) is in the Master-Detail relationship, it's likely that the roll-up summary field will be located in the master object of that relationship.

Based on additional guidance from StackExchange forum, apparently "you cannot create a master-detail relationship in which the User or Lead objects are the master".
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So it's worth keeping in mind that in this scenario the roll-up summary field may not be in the Lead object if there's a master-detail relationship created for this object, and the object isn't the master in the relationship.

Based on Salesforce's documentation: About Advanced Currency Management, if your org has enabled Advanced Currency Management (this enables multiple currencies in the org), in the source environment you'd need to delete any currency roll-up summary fields using Opportunities and Accounts, or Opportunities and Custom objects.

We hope that the use case we've described above will give you extra information to help with troubleshooting steps you can take to try to resolve this error.

For more information on the issue, please refer to below resource:

Traliblazer Community (July 2020)