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 $94.62   11.858%   $105.84   $105.84   $105.85   $105.80  
  Purchase #2 $28.85   12.159%   $32.3579   $32.36   $32.35   $32.40  
  Purchase #3 $242.32   8.486%   $262.8833   $262.88   $262.90   $262.90  
  Purchase #4 $41.28   9.173%   $45.0666   $45.07   $45.05   $45.10  
  Purchase #5 $52.99   8.343%   $57.411   $57.41   $57.40   $57.40  
  Purchase #6 $237.53   10.247%   $261.8697   $261.87   $261.85   $261.90  
  Purchase #7 $228.46   8.814%   $248.5965   $248.60   $248.60   $248.60  
  7 purchase totals = $926.05       $1,014.0250   $1,014.03   $1,014.00   $1,014.10