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 $244.40   8.735%   $265.7483   $265.75   $265.75   $265.70  
  Purchase #2 $84.69   13.477%   $96.1037   $96.10   $96.10   $96.10  
  Purchase #3 $175.81   5.206%   $184.9627   $184.96   $184.95   $185.00  
  Purchase #4 $61.25   13.532%   $69.5384   $69.54   $69.55   $69.50  
  Purchase #5 $161.34   11.173%   $179.3665   $179.37   $179.35   $179.40  
  Purchase #6 $176.75   4.595%   $184.8717   $184.87   $184.85   $184.90  
  Purchase #7 $92.30   4.818%   $96.747   $96.75   $96.75   $96.70  
  7 purchase totals = $996.54       $1,077.3383   $1,077.34   $1,077.30   $1,077.30