Grammar and Punctuation

 The police officer bit the dog; the cat ran away.  Semi colon used to connect the sentence.

 The cat ran up the tree, so the dog ran home.  Coordinating conjunction used.   

 Pat drove to the store, but I went anyway.   I used a coordinating conjunction.

 We were having fun - they wanted to have fun too.  A dash was needed to connect the two.

 Getting to work is much easier now, because I got a more reliable car.  On top of adding to the sentence, I also used a comma to show my pause between the sentence.

 Although Jim had bought a car, he was still scrambling for money.  Added to the subordinate sentence so it wouldn't stand alone.

 Jimmy played in the sandbox, while we went down the slides and on the swings.  Added to the sentence so it would no longer be a subordinate sentence.

 Whether we came home or went on to the store; it would be a lose lose situation.  Added to the sentence no longer leaving it as a subordinate sentence and joined the two.

 If I had ten dollars, we could go get ice cream.   Connected the sentence as one.

 Upon arriving at the bank, we found out that we were millionaires.  Connected both sentences as one.