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 $237.65   10.237%   $261.9782   $261.98   $262.00   $262.00  
  Purchase #2 $216.75   13.377%   $245.7446   $245.74   $245.75   $245.70  
  Purchase #3 $199.84   4.841%   $209.5143   $209.51   $209.50   $209.50  
  Purchase #4 $110.81   6.614%   $118.139   $118.14   $118.15   $118.10  
  Purchase #5 $207.40   9.770%   $227.663   $227.66   $227.65   $227.70  
  Purchase #6 $160.61   11.614%   $179.2632   $179.26   $179.25   $179.30  
  Purchase #7 $248.79   6.595%   $265.1977   $265.20   $265.20   $265.20  
  7 purchase totals = $1,381.85       $1,507.5000   $1,507.49   $1,507.50   $1,507.50