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 $77.81   11.765%   $86.9643   $86.96   $86.95   $87.00  
  Purchase #2 $115.31   3.814%   $119.7079   $119.71   $119.70   $119.70  
  Purchase #3 $196.86   10.512%   $217.5539   $217.55   $217.55   $217.60  
  Purchase #4 $239.54   3.379%   $247.6341   $247.63   $247.65   $247.60  
  Purchase #5 $103.88   10.122%   $114.3947   $114.39   $114.40   $114.40  
  Purchase #6 $189.32   12.798%   $213.5492   $213.55   $213.55   $213.50  
  Purchase #7 $64.82   11.433%   $72.2309   $72.23   $72.25   $72.20  
  7 purchase totals = $987.54       $1,072.0350   $1,072.02   $1,072.05   $1,072.00