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 $24.78   5.683%   $26.1882   $26.19   $26.20   $26.20  
  Purchase #2 $237.54   8.753%   $258.3319   $258.33   $258.35   $258.30  
  Purchase #3 $114.28   7.226%   $122.5379   $122.54   $122.55   $122.50  
  Purchase #4 $59.49   5.165%   $62.5627   $62.56   $62.55   $62.60  
  Purchase #5 $54.89   6.445%   $58.4277   $58.43   $58.45   $58.40  
  Purchase #6 $233.28   13.761%   $265.3817   $265.38   $265.40   $265.40  
  Purchase #7 $88.66   6.314%   $94.258   $94.26   $94.25   $94.30  
  7 purchase totals = $812.92       $887.6881   $887.69   $887.75   $887.70