AVR Timer/Counter Overflow and ISR
You need to configure the waveform generation mode as well in order to get this working.
Page 128 of ATmega328 Datasheet describes exactly how WGM bits need to be set.

19.5.  Output Compare Unit
The 8-bit comparator continuously compares TCNT0 with the Output Compare Registers (OCR0A and OCR0B). Whenever
TCNT0 equals OCR0A or OCR0B, the comparator signals a match. A match
will set the Output Compare Flag (OCF0A or OCF0B) at the next timer
clock cycle. If the corresponding interrupt is enabled, the Output
Compare Flag generates an Output Compare interrupt. The Output Compare
Flag is automatically cleared when the interrupt is executed.
Alternatively, the flag can be cleared by software by writing a '1' to
its I/O bit location. The Waveform Generator uses the match signal to
generate an output according to operating mode set by the WGM02,
WGM01, and WGM00 bits and Compare Output mode (COM0x[1:0]) bits. The
max and bottom signals are used by the Waveform Generator for handling
the special cases of the extreme values in some modes of operation.

This means you need to configure the TCCR0A register as well accordingly.