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 $22.95   11.266%   $25.5355   $25.54   $25.55   $25.50  
  Purchase #2 $208.25   13.695%   $236.7698   $236.77   $236.75   $236.80  
  Purchase #3 $47.62   13.847%   $54.2139   $54.21   $54.20   $54.20  
  Purchase #4 $52.35   6.512%   $55.759   $55.76   $55.75   $55.80  
  Purchase #5 $218.27   9.430%   $238.8529   $238.85   $238.85   $238.90  
  Purchase #6 $217.81   3.144%   $224.6579   $224.66   $224.65   $224.70  
  Purchase #7 $208.38   7.184%   $223.35   $223.35   $223.35   $223.40  
  7 purchase totals = $975.63       $1,059.1390   $1,059.14   $1,059.10   $1,059.30