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 $107.82   5.757%   $114.0272   $114.03   $114.05   $114.00  
  Purchase #2 $62.31   13.249%   $70.5655   $70.57   $70.55   $70.60  
  Purchase #3 $249.63   4.122%   $259.9197   $259.92   $259.90   $259.90  
  Purchase #4 $227.70   4.844%   $238.7298   $238.73   $238.75   $238.70  
  Purchase #5 $167.30   4.333%   $174.5491   $174.55   $174.55   $174.50  
  Purchase #6 $222.84   7.706%   $240.0121   $240.01   $240.00   $240.00  
  Purchase #7 $245.31   6.121%   $260.3254   $260.33   $260.35   $260.30  
  7 purchase totals = $1,282.91       $1,358.1288   $1,358.14   $1,358.15   $1,358.00