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 $56.95   11.563%   $63.5351   $63.54   $63.55   $63.50  
  Purchase #2 $179.91   3.335%   $185.91   $185.91   $185.90   $185.90  
  Purchase #3 $226.35   10.315%   $249.698   $249.70   $249.70   $249.70  
  Purchase #4 $68.73   12.623%   $77.4058   $77.41   $77.40   $77.40  
  Purchase #5 $147.81   9.383%   $161.679   $161.68   $161.70   $161.70  
  Purchase #6 $102.26   13.605%   $116.1725   $116.17   $116.15   $116.20  
  Purchase #7 $185.27   12.328%   $208.1101   $208.11   $208.10   $208.10  
  7 purchase totals = $967.28       $1,062.5105   $1,062.52   $1,062.50   $1,062.50