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 $57.32   5.136%   $60.264   $60.26   $60.25   $60.30  
  Purchase #2 $48.43   9.806%   $53.179   $53.18   $53.20   $53.20  
  Purchase #3 $13.75   10.343%   $15.1722   $15.17   $15.15   $15.20  
  Purchase #4 $158.38   9.552%   $173.5085   $173.51   $173.50   $173.50  
  Purchase #5 $59.49   3.218%   $61.4044   $61.40   $61.40   $61.40  
  Purchase #6 $22.61   7.124%   $24.2207   $24.22   $24.20   $24.20  
  Purchase #7 $161.95   9.640%   $177.562   $177.56   $177.55   $177.60  
  7 purchase totals = $521.93       $565.3108   $565.30   $565.25   $565.40