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 $220.73   10.543%   $244.0016   $244.00   $244.00   $244.00  
  Purchase #2 $62.76   8.713%   $68.2283   $68.23   $68.25   $68.20  
  Purchase #3 $42.43   3.627%   $43.9689   $43.97   $43.95   $44.00  
  Purchase #4 $240.95   11.685%   $269.105   $269.11   $269.10   $269.10  
  Purchase #5 $71.25   6.713%   $76.033   $76.03   $76.05   $76.00  
  Purchase #6 $44.25   11.836%   $49.4874   $49.49   $49.50   $49.50  
  Purchase #7 $169.99   9.530%   $186.19   $186.19   $186.20   $186.20  
  7 purchase totals = $852.36       $937.0142   $937.02   $937.05   $937.00