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 $191.38   4.869%   $200.6983   $200.70   $200.70   $200.70  
  Purchase #2 $58.77   7.491%   $63.1725   $63.17   $63.15   $63.20  
  Purchase #3 $24.73   10.344%   $27.2881   $27.29   $27.30   $27.30  
  Purchase #4 $82.94   12.634%   $93.4186   $93.42   $93.40   $93.40  
  Purchase #5 $173.85   9.624%   $190.5813   $190.58   $190.60   $190.60  
  Purchase #6 $222.25   11.305%   $247.3754   $247.38   $247.40   $247.40  
  Purchase #7 $177.71   13.188%   $201.1464   $201.15   $201.15   $201.10  
  7 purchase totals = $931.63       $1,023.6806   $1,023.69   $1,023.70   $1,023.70