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 $232.73   13.626%   $264.4418   $264.44   $264.45   $264.40  
  Purchase #2 $216.40   12.481%   $243.4089   $243.41   $243.40   $243.40  
  Purchase #3 $119.99   13.854%   $136.6134   $136.61   $136.60   $136.60  
  Purchase #4 $210.44   10.508%   $232.553   $232.55   $232.55   $232.60  
  Purchase #5 $74.70   8.859%   $81.3177   $81.32   $81.30   $81.30  
  Purchase #6 $50.53   8.791%   $54.9721   $54.97   $54.95   $55.00  
  Purchase #7 $156.70   3.201%   $161.716   $161.72   $161.70   $161.70  
  7 purchase totals = $1,061.49       $1,175.0229   $1,175.02   $1,174.95   $1,175.00