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 $114.91   10.162%   $126.5872   $126.59   $126.60   $126.60  
  Purchase #2 $63.82   4.873%   $66.9299   $66.93   $66.95   $66.90  
  Purchase #3 $52.77   7.748%   $56.8586   $56.86   $56.85   $56.90  
  Purchase #4 $129.86   13.660%   $147.5989   $147.60   $147.60   $147.60  
  Purchase #5 $144.40   3.756%   $149.8237   $149.82   $149.80   $149.80  
  Purchase #6 $74.83   12.431%   $84.1321   $84.13   $84.15   $84.10  
  Purchase #7 $114.75   4.788%   $120.2442   $120.24   $120.25   $120.20  
  7 purchase totals = $695.34       $752.1746   $752.17   $752.20   $752.10