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 $56.32   7.539%   $60.566   $60.57   $60.55   $60.60  
  Purchase #2 $196.36   7.693%   $211.466   $211.47   $211.45   $211.50  
  Purchase #3 $112.32   4.231%   $117.0723   $117.07   $117.05   $117.10  
  Purchase #4 $27.97   6.327%   $29.7397   $29.74   $29.75   $29.70  
  Purchase #5 $169.44   12.292%   $190.2676   $190.27   $190.25   $190.30  
  Purchase #6 $200.53   5.177%   $210.9114   $210.91   $210.90   $210.90  
  Purchase #7 $102.25   3.102%   $105.4218   $105.42   $105.40   $105.40  
  7 purchase totals = $865.19       $925.4448   $925.45   $925.35   $925.50