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 $171.40   13.619%   $194.743   $194.74   $194.75   $194.70  
  Purchase #2 $126.96   10.868%   $140.758   $140.76   $140.75   $140.80  
  Purchase #3 $82.94   12.724%   $93.4933   $93.49   $93.50   $93.50  
  Purchase #4 $151.56   11.650%   $169.2167   $169.22   $169.20   $169.20  
  Purchase #5 $162.87   9.314%   $178.0397   $178.04   $178.05   $178.00  
  Purchase #6 $21.81   6.153%   $23.152   $23.15   $23.15   $23.20  
  Purchase #7 $81.39   5.186%   $85.6109   $85.61   $85.60   $85.60  
  7 purchase totals = $798.93       $885.0136   $885.01   $885.00   $885.00