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 $83.58   13.114%   $94.5407   $94.54   $94.55   $94.50  
  Purchase #2 $10.46   6.698%   $11.1606   $11.16   $11.15   $11.20  
  Purchase #3 $6.73   12.230%   $7.5531   $7.55   $7.55   $7.60  
  Purchase #4 $244.90   6.342%   $260.4316   $260.43   $260.45   $260.40  
  Purchase #5 $188.30   12.457%   $211.7565   $211.76   $211.75   $211.80  
  Purchase #6 $9.47   12.543%   $10.6578   $10.66   $10.65   $10.70  
  Purchase #7 $123.80   5.584%   $130.713   $130.71   $130.70   $130.70  
  7 purchase totals = $667.24       $726.8133   $726.81   $726.80   $726.90