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 $188.36   13.586%   $213.9506   $213.95   $213.95   $214.00  
  Purchase #2 $249.43   5.443%   $263.0065   $263.01   $263.00   $263.00  
  Purchase #3 $16.32   7.710%   $17.5783   $17.58   $17.60   $17.60  
  Purchase #4 $62.38   12.157%   $69.9635   $69.96   $69.95   $70.00  
  Purchase #5 $71.64   3.115%   $73.8716   $73.87   $73.85   $73.90  
  Purchase #6 $204.34   4.664%   $213.8704   $213.87   $213.85   $213.90  
  Purchase #7 $222.50   12.198%   $249.6406   $249.64   $249.65   $249.60  
  7 purchase totals = $1,014.97       $1,101.8815   $1,101.88   $1,101.85   $1,102.00