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 $164.88   6.711%   $175.9451   $175.95   $175.95   $175.90  
  Purchase #2 $233.69   10.372%   $257.9283   $257.93   $257.95   $257.90  
  Purchase #3 $216.93   5.440%   $228.731   $228.73   $228.75   $228.70  
  Purchase #4 $168.31   13.686%   $191.3449   $191.34   $191.35   $191.30  
  Purchase #5 $217.48   10.305%   $239.8913   $239.89   $239.90   $239.90  
  Purchase #6 $235.91   7.165%   $252.813   $252.81   $252.80   $252.80  
  Purchase #7 $69.47   13.646%   $78.9499   $78.95   $78.95   $78.90  
  7 purchase totals = $1,306.67       $1,425.6035   $1,425.60   $1,425.65   $1,425.40