Either enclose the till as a cabinet, or make a chest. No other way around it. Also, for extra insurance if you enclose either way, consider one of these:https://www.amazon.com/LOCKDOWN-725741-GoldenRod-Dehumidifier-Rod/dp/B00D1WYZ1Y/ref=sr_1_1?crid=1YNF27ZF146ZX&keywords=GoldenRod+Dehumidifier+Rod&qid=1657159290&s=sporting-goods&sprefix=goldenrod+dehumidifier+rod%2Csporting%2C113&a...
they really work.
Gun safe with dehumidifier installed in the safe. I use the goldenrod.
GoldenRod 24" Dehumidifier Rod https://www.amazon.com/dp/B00D1WYZ1Y/ref=cm_sw_r_cp_apa_i_FNUXCb64R5EGT