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 $71.25   7.626%   $76.6835   $76.68   $76.70   $76.70  
  Purchase #2 $208.60   12.539%   $234.7564   $234.76   $234.75   $234.80  
  Purchase #3 $187.93   11.187%   $208.9537   $208.95   $208.95   $209.00  
  Purchase #4 $110.60   3.871%   $114.8813   $114.88   $114.90   $114.90  
  Purchase #5 $174.75   4.844%   $183.2149   $183.21   $183.20   $183.20  
  Purchase #6 $165.76   13.748%   $188.5487   $188.55   $188.55   $188.50  
  Purchase #7 $91.95   9.540%   $100.722   $100.72   $100.70   $100.70  
  7 purchase totals = $1,010.84       $1,107.7605   $1,107.75   $1,107.75   $1,107.80