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 $67.43   7.862%   $72.7313   $72.73   $72.75   $72.70  
  Purchase #2 $130.48   3.699%   $135.3065   $135.31   $135.30   $135.30  
  Purchase #3 $71.55   10.196%   $78.8452   $78.85   $78.85   $78.80  
  Purchase #4 $240.94   3.414%   $249.1657   $249.17   $249.15   $249.20  
  Purchase #5 $183.87   11.154%   $204.3789   $204.38   $204.40   $204.40  
  Purchase #6 $132.29   8.227%   $143.1735   $143.17   $143.15   $143.20  
  Purchase #7 $207.95   7.581%   $223.7147   $223.71   $223.70   $223.70  
  7 purchase totals = $1,034.51       $1,107.3158   $1,107.32   $1,107.30   $1,107.30