Step 1) First Strike Damage, the 5/5 creature dies and 2 damage rolls over.
Step 2) Combat Damage, the 7/7 is no longer blocked and does 7 to the face.
Step 3) the recipient says 'thank you ma'am may I have another'.
It will go through the first time since the 5 damage was already assigned and the extra 2 will be Trampled over to the player and on the second time since the necessary lethal damage was already applied in the 1st combat damage step, leaving the opponent with a dead 5/5 and 9 damage over him.
702.17b The controller of an attacking creature with trample first assigns damage to the creature(s) blocking it. Once all those blocking creatures are assigned lethal damage, any remaining damage is assigned as its controller chooses among those blocking creatures and the player or planeswalker the creature is attacking. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures thats being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage thats actually dealt. The attacking creatures controller need not assign lethal damage to all those blocking creatures but in that case cant assign any damage to the player or planeswalker its attacking.
702.4b If at least one attacking or blocking creature has first strike (see rule 702.7) or double strike as the combat damage step begins, the only creatures that assign combat damage in that step are those with first strike or double strike. After that step, instead of proceeding to the end of combat step, the phase gets a second combat damage step. The only creatures that assign combat damage in that step are the remaining attackers and blockers that had neither first strike nor double strike as the first combat damage step began, as well as the remaining attackers and blockers that currently have double strike. After that step, the phase proceeds to the end of combat step.