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 $61.95   5.813%   $65.5512   $65.55   $65.55   $65.60  
  Purchase #2 $56.66   10.244%   $62.4643   $62.46   $62.45   $62.50  
  Purchase #3 $165.62   5.354%   $174.4873   $174.49   $174.50   $174.50  
  Purchase #4 $147.41   11.642%   $164.5715   $164.57   $164.55   $164.60  
  Purchase #5 $240.59   8.732%   $261.5983   $261.60   $261.60   $261.60  
  Purchase #6 $118.89   4.501%   $124.2412   $124.24   $124.25   $124.20  
  Purchase #7 $84.94   8.501%   $92.1607   $92.16   $92.15   $92.20  
  7 purchase totals = $876.06       $945.0745   $945.07   $945.05   $945.20