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 $191.68   8.518%   $208.0073   $208.01   $208.00   $208.00  
  Purchase #2 $168.90   3.789%   $175.2996   $175.30   $175.30   $175.30  
  Purchase #3 $192.88   9.850%   $211.8787   $211.88   $211.90   $211.90  
  Purchase #4 $212.42   11.486%   $236.8186   $236.82   $236.80   $236.80  
  Purchase #5 $49.50   12.601%   $55.7375   $55.74   $55.75   $55.70  
  Purchase #6 $69.99   12.705%   $78.8822   $78.88   $78.90   $78.90  
  Purchase #7 $111.88   13.293%   $126.7522   $126.75   $126.75   $126.80  
  7 purchase totals = $997.25       $1,093.3761   $1,093.38   $1,093.40   $1,093.40