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 $161.42   9.198%   $176.2674   $176.27   $176.25   $176.30  
  Purchase #2 $158.81   3.119%   $163.7633   $163.76   $163.75   $163.80  
  Purchase #3 $140.30   9.459%   $153.571   $153.57   $153.55   $153.60  
  Purchase #4 $43.62   11.571%   $48.6673   $48.67   $48.65   $48.70  
  Purchase #5 $83.80   13.396%   $95.0258   $95.03   $95.05   $95.00  
  Purchase #6 $97.51   12.173%   $109.3799   $109.38   $109.40   $109.40  
  Purchase #7 $202.63   6.276%   $215.3471   $215.35   $215.35   $215.30  
  7 purchase totals = $888.09       $962.0218   $962.03   $962.00   $962.10