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 $32.63   8.863%   $35.522   $35.52   $35.50   $35.50  
  Purchase #2 $183.83   3.159%   $189.6372   $189.64   $189.65   $189.60  
  Purchase #3 $75.87   9.266%   $82.9001   $82.90   $82.90   $82.90  
  Purchase #4 $91.98   5.460%   $97.0021   $97.00   $97.00   $97.00  
  Purchase #5 $232.37   11.743%   $259.6572   $259.66   $259.65   $259.70  
  Purchase #6 $104.27   11.763%   $116.5353   $116.54   $116.55   $116.50  
  Purchase #7 $158.34   8.246%   $171.3967   $171.40   $171.40   $171.40  
  7 purchase totals = $879.29       $952.6506   $952.66   $952.65   $952.60