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 $207.61   3.427%   $214.7248   $214.72   $214.70   $214.70  
  Purchase #2 $213.84   10.342%   $235.9553   $235.96   $235.95   $236.00  
  Purchase #3 $208.55   13.639%   $236.9941   $236.99   $237.00   $237.00  
  Purchase #4 $114.42   7.175%   $122.6296   $122.63   $122.65   $122.60  
  Purchase #5 $129.81   3.115%   $133.8536   $133.85   $133.85   $133.90  
  Purchase #6 $62.61   4.336%   $65.3248   $65.32   $65.30   $65.30  
  Purchase #7 $27.97   12.796%   $31.549   $31.55   $31.55   $31.50  
  7 purchase totals = $964.81       $1,041.0312   $1,041.02   $1,041.00   $1,041.00