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 $162.69   8.321%   $176.2274   $176.23   $176.25   $176.20  
  Purchase #2 $228.67   5.541%   $241.3406   $241.34   $241.35   $241.30  
  Purchase #3 $86.29   10.554%   $95.397   $95.40   $95.40   $95.40  
  Purchase #4 $38.28   13.758%   $43.5466   $43.55   $43.55   $43.50  
  Purchase #5 $118.55   8.555%   $128.692   $128.69   $128.70   $128.70  
  Purchase #6 $240.59   12.264%   $270.096   $270.10   $270.10   $270.10  
  Purchase #7 $208.83   6.610%   $222.6337   $222.63   $222.65   $222.60  
  7 purchase totals = $1,083.90       $1,177.9333   $1,177.94   $1,178.00   $1,177.80