Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $176.61   5.857%   $186.954   $186.95   $186.95   $187.00  
  Purchase #2 $162.36   8.742%   $176.5535   $176.55   $176.55   $176.60  
  Purchase #3 $23.43   7.270%   $25.1334   $25.13   $25.15   $25.10  
  Purchase #4 $47.48   12.500%   $53.415   $53.42   $53.40   $53.40  
  Purchase #5 $107.69   3.814%   $111.7973   $111.80   $111.80   $111.80  
  Purchase #6 $199.88   7.210%   $214.2913   $214.29   $214.30   $214.30  
  Purchase #7 $37.48   12.465%   $42.1519   $42.15   $42.15   $42.20  
  7 purchase totals = $754.93       $810.2964   $810.29   $810.30   $810.40