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 $178.69   9.423%   $195.528   $195.53   $195.55   $195.50  
  Purchase #2 $88.39   10.735%   $97.8787   $97.88   $97.90   $97.90  
  Purchase #3 $196.58   5.846%   $208.0721   $208.07   $208.05   $208.10  
  Purchase #4 $5.36   10.217%   $5.9076   $5.91   $5.90   $5.90  
  Purchase #5 $181.71   5.859%   $192.3564   $192.36   $192.35   $192.40  
  Purchase #6 $242.81   6.262%   $258.0148   $258.01   $258.00   $258.00  
  Purchase #7 $164.69   5.525%   $173.7891   $173.79   $173.80   $173.80  
  7 purchase totals = $1,058.23       $1,131.5467   $1,131.55   $1,131.55   $1,131.60