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 $241.34   7.675%   $259.8628   $259.86   $259.85   $259.90  
  Purchase #2 $51.89   6.756%   $55.3957   $55.40   $55.40   $55.40  
  Purchase #3 $204.27   11.275%   $227.3014   $227.30   $227.30   $227.30  
  Purchase #4 $71.71   4.712%   $75.089   $75.09   $75.10   $75.10  
  Purchase #5 $248.92   4.139%   $259.2228   $259.22   $259.20   $259.20  
  Purchase #6 $68.42   9.169%   $74.6934   $74.69   $74.70   $74.70  
  Purchase #7 $151.50   7.241%   $162.4701   $162.47   $162.45   $162.50  
  7 purchase totals = $1,038.05       $1,114.0352   $1,114.03   $1,114.00   $1,114.10