A U.S. president may send federal soldiers to enforce order in a state primarily in the circumstance where "if a state’s police force could not keep the peace." This situation typically arises during times of civil unrest, insurrection, or when local law enforcement is overwhelmed and unable to maintain order, thereby jeopardizing public safety.
The other scenarios outlined (assisting with income tax collection, dealing with a crime committed by a state’s governor, or issues related to tolls on interstate highways) generally do not invoke the use of federal troops under the same legal framework. Federal intervention in such cases would not typically be justified under the authority to preserve order unless they escalated to a larger breakdown of law and order.