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 $241.65   5.121%   $254.0249   $254.02   $254.00   $254.00  
  Purchase #2 $105.98   8.347%   $114.8262   $114.83   $114.85   $114.80  
  Purchase #3 $207.38   3.468%   $214.5719   $214.57   $214.55   $214.60  
  Purchase #4 $99.69   4.278%   $103.9547   $103.95   $103.95   $104.00  
  Purchase #5 $226.26   8.105%   $244.5984   $244.60   $244.60   $244.60  
  Purchase #6 $158.87   7.280%   $170.4357   $170.44   $170.45   $170.40  
  Purchase #7 $12.79   11.382%   $14.2458   $14.25   $14.25   $14.20  
  7 purchase totals = $1,052.62       $1,116.6576   $1,116.66   $1,116.65   $1,116.60