Here is what I found online on the website Cemeteries and Cemetery Symbols:
This symbol, which looks like a dollar sign ($), is actually the letters I, H, and S superimposed over each other. These represent the Greek letters Iota (Ι), Eta (Η) and Sigma (Σ), which are the first three letters of Jesus in Greek. See IHS Monogram for more information.
Photo: from the grave marker of Atala Blow Noble (1862-1909) and Louis S. Noble (1865-1934), Fairmount Cemetery, Denver, Colorado