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 $235.86   11.346%   $262.6207   $262.62   $262.60   $262.60  
  Purchase #2 $59.85   13.732%   $68.0686   $68.07   $68.05   $68.10  
  Purchase #3 $209.95   8.309%   $227.3947   $227.39   $227.40   $227.40  
  Purchase #4 $208.76   6.139%   $221.5758   $221.58   $221.60   $221.60  
  Purchase #5 $58.99   10.376%   $65.1108   $65.11   $65.10   $65.10  
  Purchase #6 $143.87   13.735%   $163.6305   $163.63   $163.65   $163.60  
  Purchase #7 $56.42   7.368%   $60.577   $60.58   $60.60   $60.60  
  7 purchase totals = $973.70       $1,068.9781   $1,068.98   $1,069.00   $1,069.00