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 $63.28   8.562%   $68.698   $68.70   $68.70   $68.70  
  Purchase #2 $180.70   3.281%   $186.6288   $186.63   $186.65   $186.60  
  Purchase #3 $47.41   13.554%   $53.836   $53.84   $53.85   $53.80  
  Purchase #4 $24.39   10.642%   $26.9856   $26.99   $27.00   $27.00  
  Purchase #5 $193.66   8.370%   $209.8693   $209.87   $209.85   $209.90  
  Purchase #6 $217.36   11.540%   $242.4433   $242.44   $242.45   $242.40  
  Purchase #7 $106.31   8.760%   $115.6228   $115.62   $115.60   $115.60  
  7 purchase totals = $833.11       $904.0838   $904.09   $904.10   $904.00