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 $59.31   11.157%   $65.9272   $65.93   $65.95   $65.90  
  Purchase #2 $232.68   8.425%   $252.2833   $252.28   $252.30   $252.30  
  Purchase #3 $37.78   13.428%   $42.8531   $42.85   $42.85   $42.90  
  Purchase #4 $158.79   13.162%   $179.6899   $179.69   $179.70   $179.70  
  Purchase #5 $195.95   12.528%   $220.4986   $220.50   $220.50   $220.50  
  Purchase #6 $122.77   6.354%   $130.5708   $130.57   $130.55   $130.60  
  Purchase #7 $63.29   7.617%   $68.1108   $68.11   $68.10   $68.10  
  7 purchase totals = $870.57       $959.9337   $959.93   $959.95   $960.00