Smallmoney is 4 bytes and has a maximum of 214,748.3647

To hold the equivalent in decimal would be 9 bytes decimal(10,4)

However if you are only storing to 2 decimal places then

smallmoney would still be 4 bytes and a maximum of 214,748.3647

but numeric(9,2) is 5 bytes with a maximum of 9,999,999.99

It depends if you are worried about the extra byte or not.

If smallmoney works then use it but it would be wise to make the column name clear so that another person does not get confused and think the column is a monetary value.