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 $224.48   3.642%   $232.6556   $232.66   $232.65   $232.70  
  Purchase #2 $81.32   13.388%   $92.2071   $92.21   $92.20   $92.20  
  Purchase #3 $161.46   6.265%   $171.5755   $171.58   $171.60   $171.60  
  Purchase #4 $67.49   13.318%   $76.4783   $76.48   $76.50   $76.50  
  Purchase #5 $215.58   9.386%   $235.8143   $235.81   $235.80   $235.80  
  Purchase #6 $238.51   8.151%   $257.951   $257.95   $257.95   $258.00  
  Purchase #7 $86.54   7.699%   $93.2027   $93.20   $93.20   $93.20  
  7 purchase totals = $1,075.38       $1,159.8845   $1,159.89   $1,159.90   $1,160.00