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 $98.39   5.653%   $103.952   $103.95   $103.95   $104.00  
  Purchase #2 $204.74   3.261%   $211.4166   $211.42   $211.40   $211.40  
  Purchase #3 $108.79   4.414%   $113.592   $113.59   $113.60   $113.60  
  Purchase #4 $155.97   9.576%   $170.9057   $170.91   $170.90   $170.90  
  Purchase #5 $181.86   6.526%   $193.7282   $193.73   $193.75   $193.70  
  Purchase #6 $183.32   13.756%   $208.5375   $208.54   $208.55   $208.50  
  Purchase #7 $249.71   4.219%   $260.2453   $260.25   $260.25   $260.20  
  7 purchase totals = $1,182.78       $1,262.3773   $1,262.39   $1,262.40   $1,262.30