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 $87.88   9.154%   $95.9245   $95.92   $95.90   $95.90  
  Purchase #2 $214.64   10.115%   $236.3508   $236.35   $236.35   $236.40  
  Purchase #3 $208.70   8.791%   $227.0468   $227.05   $227.05   $227.00  
  Purchase #4 $147.89   13.515%   $167.8773   $167.88   $167.90   $167.90  
  Purchase #5 $33.87   13.313%   $38.3791   $38.38   $38.40   $38.40  
  Purchase #6 $222.40   8.801%   $241.9734   $241.97   $241.95   $242.00  
  Purchase #7 $47.90   8.856%   $52.142   $52.14   $52.15   $52.10  
  7 purchase totals = $963.28       $1,059.6939   $1,059.69   $1,059.70   $1,059.70