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 $44.67   4.688%   $46.7641   $46.76   $46.75   $46.80  
  Purchase #2 $230.90   8.426%   $250.3556   $250.36   $250.35   $250.40  
  Purchase #3 $36.40   8.497%   $39.4929   $39.49   $39.50   $39.50  
  Purchase #4 $74.40   13.719%   $84.6069   $84.61   $84.60   $84.60  
  Purchase #5 $73.55   12.287%   $82.5871   $82.59   $82.60   $82.60  
  Purchase #6 $216.28   12.125%   $242.504   $242.50   $242.50   $242.50  
  Purchase #7 $190.74   5.650%   $201.5168   $201.52   $201.50   $201.50  
  7 purchase totals = $866.94       $947.8274   $947.83   $947.80   $947.90