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 $163.54   11.316%   $182.0462   $182.05   $182.05   $182.00  
  Purchase #2 $202.76   4.355%   $211.5902   $211.59   $211.60   $211.60  
  Purchase #3 $35.68   9.831%   $39.1877   $39.19   $39.20   $39.20  
  Purchase #4 $164.69   8.451%   $178.608   $178.61   $178.60   $178.60  
  Purchase #5 $186.75   13.643%   $212.2283   $212.23   $212.25   $212.20  
  Purchase #6 $231.51   9.223%   $252.8622   $252.86   $252.85   $252.90  
  Purchase #7 $82.85   7.822%   $89.3305   $89.33   $89.35   $89.30  
  7 purchase totals = $1,067.78       $1,165.8531   $1,165.86   $1,165.90   $1,165.80