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 $226.99   9.554%   $248.6766   $248.68   $248.70   $248.70  
  Purchase #2 $213.48   6.499%   $227.3541   $227.35   $227.35   $227.40  
  Purchase #3 $6.72   3.788%   $6.9746   $6.97   $6.95   $7.00  
  Purchase #4 $67.39   5.321%   $70.9758   $70.98   $71.00   $71.00  
  Purchase #5 $242.69   9.381%   $265.4567   $265.46   $265.45   $265.50  
  Purchase #6 $60.93   10.563%   $67.366   $67.37   $67.35   $67.40  
  Purchase #7 $219.67   6.382%   $233.6893   $233.69   $233.70   $233.70  
  7 purchase totals = $1,037.87       $1,120.4931   $1,120.50   $1,120.50   $1,120.70