Find Specific Value In Array Which Appears Multiple Times And Average All Relative Cells

I'd like to search for a specific value like (1) in an array of cells like (A:A). The result needs to be the average number of a different column (B:B) in the same row as the searched value (1). And the resulting number should be rounded up to the nearest 10.

Example below: (Find value = 1 in A:A) ... 1 is found 4 times.

A | B
1 | 295
3 | 123
1 | 400
5 | 425
1 | 354
1 | 400

In the example above there are 4 (1's) found. By adding all the values in column (B) of the same row, we get 295+400+354+400 = 1449, dividing that in 4, the average is 362.25, rounding that up to the nearest 10... THE RESULT I'M LOOKING FOR IS: 370