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 $205.99   4.499%   $215.2575   $215.26   $215.25   $215.30  
  Purchase #2 $190.42   6.551%   $202.8944   $202.89   $202.90   $202.90  
  Purchase #3 $53.37   12.754%   $60.1768   $60.18   $60.20   $60.20  
  Purchase #4 $208.35   5.157%   $219.0946   $219.09   $219.10   $219.10  
  Purchase #5 $136.86   10.463%   $151.1797   $151.18   $151.20   $151.20  
  Purchase #6 $155.79   8.393%   $168.8655   $168.87   $168.85   $168.90  
  Purchase #7 $190.57   3.311%   $196.8798   $196.88   $196.90   $196.90  
  7 purchase totals = $1,141.35       $1,214.3483   $1,214.35   $1,214.40   $1,214.50