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 $44.67   8.850%   $48.6233   $48.62   $48.60   $48.60  
  Purchase #2 $246.68   8.118%   $266.7055   $266.71   $266.70   $266.70  
  Purchase #3 $87.78   13.122%   $99.2985   $99.30   $99.30   $99.30  
  Purchase #4 $102.69   6.686%   $109.5559   $109.56   $109.55   $109.60  
  Purchase #5 $43.63   7.557%   $46.9271   $46.93   $46.95   $46.90  
  Purchase #6 $227.71   5.602%   $240.4663   $240.47   $240.45   $240.50  
  Purchase #7 $55.51   3.671%   $57.5478   $57.55   $57.55   $57.50  
  7 purchase totals = $808.67       $869.1244   $869.14   $869.10   $869.10