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 $41.47   12.517%   $46.6608   $46.66   $46.65   $46.70  
  Purchase #2 $214.72   3.767%   $222.8085   $222.81   $222.80   $222.80  
  Purchase #3 $46.32   11.118%   $51.4699   $51.47   $51.45   $51.50  
  Purchase #4 $245.60   12.659%   $276.6905   $276.69   $276.70   $276.70  
  Purchase #5 $227.72   13.149%   $257.6629   $257.66   $257.65   $257.70  
  Purchase #6 $111.90   3.169%   $115.4461   $115.45   $115.45   $115.40  
  Purchase #7 $69.75   5.825%   $73.8129   $73.81   $73.80   $73.80  
  7 purchase totals = $957.48       $1,044.5516   $1,044.55   $1,044.50   $1,044.60