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 $196.51   6.322%   $208.9334   $208.93   $208.95   $208.90  
  Purchase #2 $232.41   11.742%   $259.6996   $259.70   $259.70   $259.70  
  Purchase #3 $112.27   5.806%   $118.7884   $118.79   $118.80   $118.80  
  Purchase #4 $172.99   11.596%   $193.0499   $193.05   $193.05   $193.00  
  Purchase #5 $198.48   11.323%   $220.9539   $220.95   $220.95   $221.00  
  Purchase #6 $112.92   9.394%   $123.5277   $123.53   $123.55   $123.50  
  Purchase #7 $156.77   3.365%   $162.0453   $162.05   $162.05   $162.00  
  7 purchase totals = $1,182.35       $1,286.9982   $1,287.00   $1,287.05   $1,286.90