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 $98.57   8.534%   $106.982   $106.98   $107.00   $107.00  
  Purchase #2 $128.99   8.812%   $140.3566   $140.36   $140.35   $140.40  
  Purchase #3 $168.45   8.404%   $182.6065   $182.61   $182.60   $182.60  
  Purchase #4 $249.66   13.760%   $284.0132   $284.01   $284.00   $284.00  
  Purchase #5 $28.44   5.611%   $30.0358   $30.04   $30.05   $30.00  
  Purchase #6 $228.97   13.309%   $259.4436   $259.44   $259.45   $259.40  
  Purchase #7 $53.80   8.872%   $58.5731   $58.57   $58.55   $58.60  
  7 purchase totals = $956.88       $1,062.0108   $1,062.01   $1,062.00   $1,062.00