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 $176.76   10.136%   $194.6764   $194.68   $194.70   $194.70  
  Purchase #2 $245.35   6.416%   $261.0917   $261.09   $261.10   $261.10  
  Purchase #3 $197.71   10.341%   $218.1552   $218.16   $218.15   $218.20  
  Purchase #4 $86.81   13.671%   $98.6778   $98.68   $98.70   $98.70  
  Purchase #5 $193.31   13.749%   $219.8882   $219.89   $219.90   $219.90  
  Purchase #6 $198.74   6.332%   $211.3242   $211.32   $211.30   $211.30  
  Purchase #7 $76.30   3.118%   $78.679   $78.68   $78.70   $78.70  
  7 purchase totals = $1,174.98       $1,282.4925   $1,282.50   $1,282.55   $1,282.60