Doesn’t buying extraneous dump trucks make your trash-hauling business look bigger? You’d have to make it look like you’re using the industry-typical amount of money for insurance, maintenance, payroll etc for your ‘larger’ business. Then you can get away with more fake customers/pickups before tripping any red flags.
I image that trash-hauling expenses are mostly capital equipment and payroll. Heck, you could provide ‘legitimate employment’ as ‘drivers’ to your mob underlings to help with their money laundering problems. You wouldn’t want all your underlings doing their own amateur money laundering and getting caught; they might rat you out!