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 $111.48   5.570%   $117.6894   $117.69   $117.70   $117.70  
  Purchase #2 $182.67   8.755%   $198.6628   $198.66   $198.65   $198.70  
  Purchase #3 $73.67   8.178%   $79.6947   $79.69   $79.70   $79.70  
  Purchase #4 $225.72   13.788%   $256.8423   $256.84   $256.85   $256.80  
  Purchase #5 $82.68   4.531%   $86.4262   $86.43   $86.45   $86.40  
  Purchase #6 $197.71   9.228%   $215.9547   $215.95   $215.95   $216.00  
  Purchase #7 $98.76   10.769%   $109.3955   $109.40   $109.40   $109.40  
  7 purchase totals = $972.69       $1,064.6656   $1,064.66   $1,064.70   $1,064.70