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 $62.61   7.615%   $67.3778   $67.38   $67.40   $67.40  
  Purchase #2 $152.46   12.618%   $171.6974   $171.70   $171.70   $171.70  
  Purchase #3 $180.63   8.339%   $195.6927   $195.69   $195.70   $195.70  
  Purchase #4 $125.75   12.210%   $141.1041   $141.10   $141.10   $141.10  
  Purchase #5 $68.46   3.127%   $70.6007   $70.60   $70.60   $70.60  
  Purchase #6 $141.34   8.698%   $153.6338   $153.63   $153.65   $153.60  
  Purchase #7 $193.30   4.387%   $201.7801   $201.78   $201.80   $201.80  
  7 purchase totals = $924.55       $1,001.8866   $1,001.88   $1,001.95   $1,001.90