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 $166.59   5.445%   $175.6608   $175.66   $175.65   $175.70  
  Purchase #2 $208.78   13.347%   $236.6459   $236.65   $236.65   $236.60  
  Purchase #3 $23.92   3.347%   $24.7206   $24.72   $24.70   $24.70  
  Purchase #4 $125.46   6.304%   $133.369   $133.37   $133.35   $133.40  
  Purchase #5 $81.32   4.249%   $84.7753   $84.78   $84.80   $84.80  
  Purchase #6 $23.49   6.843%   $25.0974   $25.10   $25.10   $25.10  
  Purchase #7 $47.43   11.727%   $52.9921   $52.99   $53.00   $53.00  
  7 purchase totals = $676.99       $733.2611   $733.27   $733.25   $733.30