The solution by Jannet is probably the best you can get, because there is no other discerning field for identifying individual records.
If on the other hand, you want to keep just the sum of the individual fields (in QlikView terms, there is no difference at all between the two solutions if you aggregate by [SALES ID] except when processing huge numbers os rows = script execution takes longer, UI responses come quicker), you can just throw the various fields together row-by-row, like in:
LOAD [SALES ID],
[Paid In Account],
[Paid Cash] + [Paid Card] + [On Account] + [Paid Cheque] +[Paid In Account]) as [Total Paid]
Sum([Total Paid]) will produce the same result in both cases.
PS Use RangeSum() if you want to avoid getting a NULL value as total if any single field contains Null.