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 $61.51   13.124%   $69.5826   $69.58   $69.60   $69.60  
  Purchase #2 $64.98   4.602%   $67.9704   $67.97   $67.95   $68.00  
  Purchase #3 $53.35   12.263%   $59.8923   $59.89   $59.90   $59.90  
  Purchase #4 $57.72   5.515%   $60.9033   $60.90   $60.90   $60.90  
  Purchase #5 $222.63   5.426%   $234.7099   $234.71   $234.70   $234.70  
  Purchase #6 $154.52   10.848%   $171.2823   $171.28   $171.30   $171.30  
  Purchase #7 $218.61   6.404%   $232.6098   $232.61   $232.60   $232.60  
  7 purchase totals = $833.32       $896.9506   $896.94   $896.95   $897.00