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 $44.43   4.598%   $46.4729   $46.47   $46.45   $46.50  
  Purchase #2 $199.95   9.168%   $218.2814   $218.28   $218.30   $218.30  
  Purchase #3 $25.27   7.202%   $27.0899   $27.09   $27.10   $27.10  
  Purchase #4 $247.87   5.443%   $261.3616   $261.36   $261.35   $261.40  
  Purchase #5 $231.51   6.544%   $246.66   $246.66   $246.65   $246.70  
  Purchase #6 $90.26   4.354%   $94.1899   $94.19   $94.20   $94.20  
  Purchase #7 $231.84   4.450%   $242.1569   $242.16   $242.15   $242.20  
  7 purchase totals = $1,071.13       $1,136.2126   $1,136.21   $1,136.20   $1,136.40