All Tetra and Marineland open glass aquariums from 2.5-40g are on sale for $1/gallon at PetSmart. The sale is in-store only. Our area was hit hard with tank purchases during the pandemic and many are OOS, so YMMV.
You can check a few using these links (Again, sale prices not reflected online.):
Tetra 2.5g [petsmart.com]
Tetra 10g [petsmart.com]
Tetra 20g [petsmart.com]
Tetra 40g [petsmart.com]
Unlike Petco, this sale includes 2.5g, 5g, and 40g tanks.
Petco is rumored to be having their $1/gallon (10-29g) Aqueon sale (Read it here on SD. Thanks, swineflu22.) this Sunday, 07/12. Other Aqueon tanks should be 50% off. In March, Petco's 40g was $50 and their 55g was $70.