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 $105.51   8.105%   $114.0616   $114.06   $114.05   $114.10  
  Purchase #2 $230.74   8.648%   $250.6944   $250.69   $250.70   $250.70  
  Purchase #3 $61.90   11.116%   $68.7808   $68.78   $68.80   $68.80  
  Purchase #4 $199.82   7.343%   $214.4928   $214.49   $214.50   $214.50  
  Purchase #5 $69.62   10.145%   $76.6829   $76.68   $76.70   $76.70  
  Purchase #6 $85.44   7.349%   $91.719   $91.72   $91.70   $91.70  
  Purchase #7 $192.57   8.477%   $208.8942   $208.89   $208.90   $208.90  
  7 purchase totals = $945.60       $1,025.3257   $1,025.31   $1,025.35   $1,025.40