CALCULATE is defined as CALCULATE(<expression>,<filter1>,<filter2>…) This means that you can use multiple filters at one time. However, multiple filters will act at the same time. Meaning that the data would have to meet both conditions.
So doing BadSumOfSales:=CALCULATE([Sum of Sales],Table3[SKU]="A1",Table4[SKU]="AB") will not give you what you need. Since the SKU would have to be equal to A1 and AB, it will return blank
Since you have five items you would like to included in your filtering, you should leverage the SWITCH function. This will allow you to accommodate multiple conditions that should return TRUE and then let you return FALSE for anything else
TotalsSumOfSales:=CALCULATE([Sum Of Sales],
Another way to get around this would be using the OR function. This is a great option, but only really works well when you have two filters at a time. If you have more than two, you will have to do some nesting that can get complex. So for your case I would stick with the SWITCH, but here is an example of how it would look:
OrTotalSumOfSales:=CALCULATE([Sum of Sales],