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 $89.61   6.781%   $95.6865   $95.69   $95.70   $95.70  
  Purchase #2 $239.47   5.475%   $252.581   $252.58   $252.60   $252.60  
  Purchase #3 $118.37   12.356%   $132.9958   $133.00   $133.00   $133.00  
  Purchase #4 $154.50   7.619%   $166.2714   $166.27   $166.25   $166.30  
  Purchase #5 $136.47   13.474%   $154.858   $154.86   $154.85   $154.90  
  Purchase #6 $163.42   7.496%   $175.67   $175.67   $175.65   $175.70  
  Purchase #7 $164.26   8.218%   $177.7589   $177.76   $177.75   $177.80  
  7 purchase totals = $1,066.10       $1,155.8216   $1,155.83   $1,155.80   $1,156.00