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 $62.93   9.125%   $68.6724   $68.67   $68.65   $68.70  
  Purchase #2 $237.41   6.348%   $252.4808   $252.48   $252.50   $252.50  
  Purchase #3 $164.70   10.676%   $182.2834   $182.28   $182.30   $182.30  
  Purchase #4 $42.96   9.304%   $46.957   $46.96   $46.95   $47.00  
  Purchase #5 $183.93   11.393%   $204.8851   $204.89   $204.90   $204.90  
  Purchase #6 $19.52   6.170%   $20.7244   $20.72   $20.70   $20.70  
  Purchase #7 $170.62   9.247%   $186.3972   $186.40   $186.40   $186.40  
  7 purchase totals = $882.07       $962.4003   $962.40   $962.40   $962.50