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 $54.47   12.800%   $61.4422   $61.44   $61.45   $61.40  
  Purchase #2 $68.71   10.788%   $76.1224   $76.12   $76.10   $76.10  
  Purchase #3 $213.82   4.691%   $223.8503   $223.85   $223.85   $223.90  
  Purchase #4 $46.51   13.223%   $52.66   $52.66   $52.65   $52.70  
  Purchase #5 $239.56   9.305%   $261.8511   $261.85   $261.85   $261.90  
  Purchase #6 $200.35   8.631%   $217.6422   $217.64   $217.65   $217.60  
  Purchase #7 $108.66   8.608%   $118.0135   $118.01   $118.00   $118.00  
  7 purchase totals = $932.08       $1,011.5817   $1,011.57   $1,011.55   $1,011.60