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 $46.60   11.667%   $52.0368   $52.04   $52.05   $52.00  
  Purchase #2 $95.66   12.319%   $107.4444   $107.44   $107.45   $107.40  
  Purchase #3 $231.49   5.544%   $244.3238   $244.32   $244.30   $244.30  
  Purchase #4 $66.71   3.615%   $69.1216   $69.12   $69.10   $69.10  
  Purchase #5 $230.53   13.554%   $261.776   $261.78   $261.80   $261.80  
  Purchase #6 $241.91   7.143%   $259.1896   $259.19   $259.20   $259.20  
  Purchase #7 $70.83   10.392%   $78.1907   $78.19   $78.20   $78.20  
  7 purchase totals = $983.73       $1,072.0829   $1,072.08   $1,072.10   $1,072.00