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 $43.49   7.704%   $46.8405   $46.84   $46.85   $46.80  
  Purchase #2 $196.52   10.326%   $216.8127   $216.81   $216.80   $216.80  
  Purchase #3 $12.78   8.478%   $13.8635   $13.86   $13.85   $13.90  
  Purchase #4 $240.74   8.623%   $261.499   $261.50   $261.50   $261.50  
  Purchase #5 $173.80   11.654%   $194.0547   $194.05   $194.05   $194.10  
  Purchase #6 $150.57   9.397%   $164.7191   $164.72   $164.70   $164.70  
  Purchase #7 $206.38   13.496%   $234.233   $234.23   $234.25   $234.20  
  7 purchase totals = $1,024.28       $1,132.0225   $1,132.01   $1,132.00   $1,132.00