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 $57.61   9.685%   $63.1895   $63.19   $63.20   $63.20  
  Purchase #2 $174.96   3.313%   $180.7564   $180.76   $180.75   $180.80  
  Purchase #3 $162.32   5.801%   $171.7362   $171.74   $171.75   $171.70  
  Purchase #4 $248.28   11.328%   $276.4052   $276.41   $276.40   $276.40  
  Purchase #5 $109.93   13.198%   $124.4386   $124.44   $124.45   $124.40  
  Purchase #6 $224.61   11.741%   $250.9815   $250.98   $251.00   $251.00  
  Purchase #7 $7.62   4.241%   $7.9432   $7.94   $7.95   $7.90  
  7 purchase totals = $985.33       $1,075.4506   $1,075.46   $1,075.50   $1,075.40