Your formula will work fine, what the Sum is superfluous.
Also when testing a bully and checkbox field that checkbox field is either true or false inherently so you don't really have to test it against true. For example this is the same thing as I originally wrote just more verbose. I do recognize it's probably easier to read the way you wrote it. (aside form the superfluous SUM( )
If([Field1]=true, 676.54, 0)
+If([Field2]=true, 71.64, 0)
+If([Field3]=true, 286.47,0)
+If([Field4]=true, 297.62, 0)
+If([Field5]=true, 297.62, 0)
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Mark Shnier (Your Quickbase Coach)
mark.shnier@gmail.com
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