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 $211.94   9.498%   $232.0701   $232.07   $232.05   $232.10  
  Purchase #2 $124.56   10.659%   $137.8369   $137.84   $137.85   $137.80  
  Purchase #3 $112.97   12.796%   $127.4256   $127.43   $127.45   $127.40  
  Purchase #4 $103.30   3.773%   $107.1975   $107.20   $107.20   $107.20  
  Purchase #5 $219.95   8.762%   $239.222   $239.22   $239.20   $239.20  
  Purchase #6 $96.30   5.168%   $101.2768   $101.28   $101.30   $101.30  
  Purchase #7 $90.48   8.554%   $98.2197   $98.22   $98.20   $98.20  
  7 purchase totals = $959.50       $1,043.2486   $1,043.26   $1,043.25   $1,043.20