Yes, they can both mean the same thing, "to take care of".
But be careful of additional meanings of these words...
"Tend to" can also mean "has a tendency to"...
Ex. - "He tends to enjoy coffee more than tea."
Ex. - "He tends to leave work at 5pm instead of 6pm."
"Attend" can also mean "visit"...
Ex. - "The girl attends a meeting every Wednesday."
Ex. - "I want to attend a concert some day."