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 $244.63   7.362%   $262.6397   $262.64   $262.65   $262.60  
  Purchase #2 $238.31   4.246%   $248.4286   $248.43   $248.45   $248.40  
  Purchase #3 $230.25   8.748%   $250.3923   $250.39   $250.40   $250.40  
  Purchase #4 $59.26   4.268%   $61.7892   $61.79   $61.80   $61.80  
  Purchase #5 $179.38   7.305%   $192.4837   $192.48   $192.50   $192.50  
  Purchase #6 $69.50   12.105%   $77.913   $77.91   $77.90   $77.90  
  Purchase #7 $105.80   4.399%   $110.4541   $110.45   $110.45   $110.50  
  7 purchase totals = $1,127.13       $1,204.1006   $1,204.09   $1,204.15   $1,204.10