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 $214.71   13.642%   $244.0007   $244.00   $244.00   $244.00  
  Purchase #2 $58.42   8.624%   $63.4581   $63.46   $63.45   $63.50  
  Purchase #3 $160.74   12.219%   $180.3808   $180.38   $180.40   $180.40  
  Purchase #4 $207.63   5.322%   $218.6801   $218.68   $218.70   $218.70  
  Purchase #5 $162.88   10.129%   $179.3781   $179.38   $179.40   $179.40  
  Purchase #6 $24.97   13.618%   $28.3704   $28.37   $28.35   $28.40  
  Purchase #7 $110.63   3.429%   $114.4235   $114.42   $114.40   $114.40  
  7 purchase totals = $939.98       $1,028.6917   $1,028.69   $1,028.70   $1,028.80