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 $46.50   3.808%   $48.2707   $48.27   $48.25   $48.30  
  Purchase #2 $195.38   6.455%   $207.9918   $207.99   $208.00   $208.00  
  Purchase #3 $92.25   13.592%   $104.7886   $104.79   $104.80   $104.80  
  Purchase #4 $97.57   9.224%   $106.5699   $106.57   $106.55   $106.60  
  Purchase #5 $190.85   3.273%   $197.0965   $197.10   $197.10   $197.10  
  Purchase #6 $246.83   3.371%   $255.1506   $255.15   $255.15   $255.20  
  Purchase #7 $112.59   8.387%   $122.0329   $122.03   $122.05   $122.00  
  7 purchase totals = $981.97       $1,041.9010   $1,041.90   $1,041.90   $1,042.00