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 $194.27   11.839%   $217.2696   $217.27   $217.25   $217.30  
  Purchase #2 $247.98   5.476%   $261.5594   $261.56   $261.55   $261.60  
  Purchase #3 $155.41   12.724%   $175.1844   $175.18   $175.20   $175.20  
  Purchase #4 $16.82   8.527%   $18.2542   $18.25   $18.25   $18.30  
  Purchase #5 $208.78   10.815%   $231.3596   $231.36   $231.35   $231.40  
  Purchase #6 $204.89   10.577%   $226.5612   $226.56   $226.55   $226.60  
  Purchase #7 $5.48   10.829%   $6.0734   $6.07   $6.05   $6.10  
  7 purchase totals = $1,033.63       $1,136.2618   $1,136.25   $1,136.20   $1,136.50