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 $85.76   10.798%   $95.0204   $95.02   $95.00   $95.00  
  Purchase #2 $195.32   9.855%   $214.5688   $214.57   $214.55   $214.60  
  Purchase #3 $106.40   7.637%   $114.5258   $114.53   $114.55   $114.50  
  Purchase #4 $57.45   9.224%   $62.7492   $62.75   $62.75   $62.70  
  Purchase #5 $176.69   9.775%   $193.9614   $193.96   $193.95   $194.00  
  Purchase #6 $191.57   9.543%   $209.8515   $209.85   $209.85   $209.90  
  Purchase #7 $85.56   7.181%   $91.7041   $91.70   $91.70   $91.70  
  7 purchase totals = $898.75       $982.3812   $982.38   $982.35   $982.40