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 $191.28   9.866%   $210.1517   $210.15   $210.15   $210.20  
  Purchase #2 $98.53   4.223%   $102.6909   $102.69   $102.70   $102.70  
  Purchase #3 $169.93   4.520%   $177.6108   $177.61   $177.60   $177.60  
  Purchase #4 $110.70   12.382%   $124.4069   $124.41   $124.40   $124.40  
  Purchase #5 $228.44   3.686%   $236.8603   $236.86   $236.85   $236.90  
  Purchase #6 $151.75   9.128%   $165.6017   $165.60   $165.60   $165.60  
  Purchase #7 $223.66   9.493%   $244.892   $244.89   $244.90   $244.90  
  7 purchase totals = $1,174.29       $1,262.2143   $1,262.21   $1,262.20   $1,262.30