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 $206.62   3.867%   $214.61   $214.61   $214.60   $214.60  
  Purchase #2 $82.92   13.706%   $94.285   $94.29   $94.30   $94.30  
  Purchase #3 $88.83   10.677%   $98.3144   $98.31   $98.30   $98.30  
  Purchase #4 $248.99   3.611%   $257.981   $257.98   $258.00   $258.00  
  Purchase #5 $46.27   12.270%   $51.9473   $51.95   $51.95   $51.90  
  Purchase #6 $207.43   6.743%   $221.417   $221.42   $221.40   $221.40  
  Purchase #7 $186.66   9.294%   $204.0082   $204.01   $204.00   $204.00  
  7 purchase totals = $1,067.72       $1,142.5629   $1,142.57   $1,142.55   $1,142.50