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 $42.76   13.182%   $48.3966   $48.40   $48.40   $48.40  
  Purchase #2 $149.25   8.572%   $162.0437   $162.04   $162.05   $162.00  
  Purchase #3 $108.46   9.770%   $119.0565   $119.06   $119.05   $119.10  
  Purchase #4 $241.51   8.275%   $261.495   $261.50   $261.50   $261.50  
  Purchase #5 $214.69   10.323%   $236.8524   $236.85   $236.85   $236.90  
  Purchase #6 $151.61   7.579%   $163.1005   $163.10   $163.10   $163.10  
  Purchase #7 $205.30   4.535%   $214.6104   $214.61   $214.60   $214.60  
  7 purchase totals = $1,113.58       $1,205.5551   $1,205.56   $1,205.55   $1,205.60