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 $208.86   12.558%   $235.0886   $235.09   $235.10   $235.10  
  Purchase #2 $212.93   9.459%   $233.071   $233.07   $233.05   $233.10  
  Purchase #3 $63.38   9.526%   $69.4176   $69.42   $69.40   $69.40  
  Purchase #4 $145.88   11.785%   $163.072   $163.07   $163.05   $163.10  
  Purchase #5 $119.27   6.624%   $127.1704   $127.17   $127.15   $127.20  
  Purchase #6 $110.56   3.784%   $114.7436   $114.74   $114.75   $114.70  
  Purchase #7 $173.66   9.749%   $190.5901   $190.59   $190.60   $190.60  
  7 purchase totals = $1,034.54       $1,133.1533   $1,133.15   $1,133.10   $1,133.20