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 $109.58   4.161%   $114.1396   $114.14   $114.15   $114.10  
  Purchase #2 $145.31   5.407%   $153.1669   $153.17   $153.15   $153.20  
  Purchase #3 $245.98   5.654%   $259.8877   $259.89   $259.90   $259.90  
  Purchase #4 $242.86   13.397%   $275.396   $275.40   $275.40   $275.40  
  Purchase #5 $8.94   11.443%   $9.963   $9.96   $9.95   $10.00  
  Purchase #6 $107.69   7.594%   $115.868   $115.87   $115.85   $115.90  
  Purchase #7 $227.48   12.321%   $255.5078   $255.51   $255.50   $255.50  
  7 purchase totals = $1,087.84       $1,183.9290   $1,183.94   $1,183.90   $1,184.00