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 $37.94   13.372%   $43.0133   $43.01   $43.00   $43.00  
  Purchase #2 $114.72   4.363%   $119.7252   $119.73   $119.75   $119.70  
  Purchase #3 $27.76   13.661%   $31.5523   $31.55   $31.55   $31.60  
  Purchase #4 $67.60   4.536%   $70.6663   $70.67   $70.65   $70.70  
  Purchase #5 $48.51   4.253%   $50.5731   $50.57   $50.55   $50.60  
  Purchase #6 $163.66   6.574%   $174.419   $174.42   $174.40   $174.40  
  Purchase #7 $224.55   8.579%   $243.8141   $243.81   $243.80   $243.80  
  7 purchase totals = $684.74       $733.7633   $733.76   $733.70   $733.80