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 $62.59   11.407%   $69.7296   $69.73   $69.75   $69.70  
  Purchase #2 $245.39   5.666%   $259.2938   $259.29   $259.30   $259.30  
  Purchase #3 $216.67   3.749%   $224.793   $224.79   $224.80   $224.80  
  Purchase #4 $203.28   11.705%   $227.0739   $227.07   $227.05   $227.10  
  Purchase #5 $90.32   13.559%   $102.5665   $102.57   $102.55   $102.60  
  Purchase #6 $159.49   9.863%   $175.2205   $175.22   $175.20   $175.20  
  Purchase #7 $74.46   5.625%   $78.6484   $78.65   $78.65   $78.60  
  7 purchase totals = $1,052.20       $1,137.3257   $1,137.32   $1,137.30   $1,137.30