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 $250.84   4.355%   $261.7641   $261.76   $261.75   $261.80  
  Purchase #2 $214.84   4.218%   $223.902   $223.90   $223.90   $223.90  
  Purchase #3 $244.34   4.223%   $254.6585   $254.66   $254.65   $254.70  
  Purchase #4 $219.32   3.103%   $226.1255   $226.13   $226.15   $226.10  
  Purchase #5 $18.73   11.790%   $20.9383   $20.94   $20.95   $20.90  
  Purchase #6 $51.70   6.267%   $54.94   $54.94   $54.95   $54.90  
  Purchase #7 $84.48   9.713%   $92.6855   $92.69   $92.70   $92.70  
  7 purchase totals = $1,084.25       $1,135.0139   $1,135.02   $1,135.05   $1,135.00