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 $191.42   8.636%   $207.951   $207.95   $207.95   $208.00  
  Purchase #2 $133.34   5.844%   $141.1324   $141.13   $141.15   $141.10  
  Purchase #3 $104.25   9.820%   $114.4874   $114.49   $114.50   $114.50  
  Purchase #4 $60.25   3.298%   $62.237   $62.24   $62.25   $62.20  
  Purchase #5 $178.63   7.226%   $191.5378   $191.54   $191.55   $191.50  
  Purchase #6 $59.50   11.516%   $66.352   $66.35   $66.35   $66.40  
  Purchase #7 $75.48   6.626%   $80.4813   $80.48   $80.50   $80.50  
  7 purchase totals = $802.87       $864.1789   $864.18   $864.25   $864.20