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 $59.53   7.368%   $63.9162   $63.92   $63.90   $63.90  
  Purchase #2 $156.46   3.792%   $162.393   $162.39   $162.40   $162.40  
  Purchase #3 $118.87   3.497%   $123.0269   $123.03   $123.05   $123.00  
  Purchase #4 $231.61   7.239%   $248.3762   $248.38   $248.40   $248.40  
  Purchase #5 $125.67   7.460%   $135.045   $135.05   $135.05   $135.00  
  Purchase #6 $174.46   6.115%   $185.1282   $185.13   $185.15   $185.10  
  Purchase #7 $121.73   10.642%   $134.6845   $134.68   $134.70   $134.70  
  7 purchase totals = $988.33       $1,052.5700   $1,052.58   $1,052.65   $1,052.50