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 $113.38   5.189%   $119.2633   $119.26   $119.25   $119.30  
  Purchase #2 $249.84   4.512%   $261.1128   $261.11   $261.10   $261.10  
  Purchase #3 $169.39   11.786%   $189.3543   $189.35   $189.35   $189.40  
  Purchase #4 $173.38   11.565%   $193.4314   $193.43   $193.45   $193.40  
  Purchase #5 $48.28   10.683%   $53.4378   $53.44   $53.45   $53.40  
  Purchase #6 $180.26   10.151%   $198.5582   $198.56   $198.55   $198.60  
  Purchase #7 $40.86   5.767%   $43.2164   $43.22   $43.20   $43.20  
  7 purchase totals = $975.39       $1,058.3742   $1,058.37   $1,058.35   $1,058.40