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 $56.45   9.605%   $61.872   $61.87   $61.85   $61.90  
  Purchase #2 $66.48   3.800%   $69.0062   $69.01   $69.00   $69.00  
  Purchase #3 $42.32   10.403%   $46.7225   $46.72   $46.70   $46.70  
  Purchase #4 $154.71   4.494%   $161.6627   $161.66   $161.65   $161.70  
  Purchase #5 $176.62   12.354%   $198.4396   $198.44   $198.45   $198.40  
  Purchase #6 $200.88   12.510%   $226.0101   $226.01   $226.00   $226.00  
  Purchase #7 $97.31   11.585%   $108.5834   $108.58   $108.60   $108.60  
  7 purchase totals = $794.77       $872.2965   $872.29   $872.25   $872.30