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 $41.73   5.309%   $43.9454   $43.95   $43.95   $43.90  
  Purchase #2 $111.45   3.466%   $115.3129   $115.31   $115.30   $115.30  
  Purchase #3 $22.25   3.558%   $23.0417   $23.04   $23.05   $23.00  
  Purchase #4 $234.52   4.335%   $244.6864   $244.69   $244.70   $244.70  
  Purchase #5 $17.51   5.553%   $18.4823   $18.48   $18.50   $18.50  
  Purchase #6 $250.31   3.829%   $259.8944   $259.89   $259.90   $259.90  
  Purchase #7 $116.94   5.651%   $123.5483   $123.55   $123.55   $123.50  
  7 purchase totals = $794.71       $828.9114   $828.91   $828.95   $828.80