These differences are brought about by the need to round off cents to shillings. The value of cents is so low that it is no longer used in certain countries like Kenya or Tanzania. Subsequently, you cannot send amounts in cents.
For this reason, we round up the cents (decimals) to a shilling.
If 1 GBP = 150.65 KES (We round the 150.65 KES to give you 151 KES)
If 10 GBP = 1,506. 5 KES (You can't send 0.5 KES then we round it up to give 1,507 KES)
If 100 GBP = 15,065 KES (We don't round up here because there's no fraction of a shilling)
Alternatively, the figures can be rounded down if its less than .50 e.g. 1 GBP = 150.21 KES becomes 150.00 KES