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 $242.57   7.824%   $261.5487   $261.55   $261.55   $261.50  
  Purchase #2 $211.49   6.709%   $225.6789   $225.68   $225.70   $225.70  
  Purchase #3 $187.34   4.168%   $195.1483   $195.15   $195.15   $195.10  
  Purchase #4 $157.82   12.761%   $177.9594   $177.96   $177.95   $178.00  
  Purchase #5 $56.61   4.136%   $58.9514   $58.95   $58.95   $59.00  
  Purchase #6 $43.76   5.711%   $46.2591   $46.26   $46.25   $46.30  
  Purchase #7 $69.74   8.233%   $75.4817   $75.48   $75.50   $75.50  
  7 purchase totals = $969.33       $1,041.0275   $1,041.03   $1,041.05   $1,041.10