I think that it only makes good sense to take your total weekly dose and divide it by 7, so that you can take the SAME dose daily. With the many different dosages available - from 1 mg pills that you can split in half, to 2, 2.5, 5, 7.5, and probably others, it shouldn't be too difficult to tailor your daily dosing to be almost the same every day. With generic warfarin available at about a dime a pill, the cost of taking two pills (or two half pills?) a day isn't that high.
OTOH -- the scenario that you describe - taking 5 mg five days and 7.5 mg two days isn't that terrible, either. If you do the 7.5 three or four days apart (maybe Monday and Thursday or Friday), the effects should be fairly balanced all week. In the past, I've done something similar, taking one dose on days with at 'T' in their name, and another dose for all the other days. The idea is to try and do the same dose every day - but to try and keep it simple (or to use a weekly pill dispenser to keep track).
(One thought -- in your specific case, when you're taking 60 mg/week, why not take a 7.5 mg plus a 1 mg every day? Getting to 59.5 this way is awfully close to your target of 60 and is easy to do, and may be even easier to remember because you're taking the same dose EVERY day. Plus, this will balance out your dosages a lot more evenly. If you MUST have 60 mg, you can always break a 1 mg pill in half and add it one day during the week).