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 $182.87   10.867%   $202.7425   $202.74   $202.75   $202.70  
  Purchase #2 $130.41   12.422%   $146.6095   $146.61   $146.60   $146.60  
  Purchase #3 $95.68   3.357%   $98.892   $98.89   $98.90   $98.90  
  Purchase #4 $46.73   3.257%   $48.252   $48.25   $48.25   $48.30  
  Purchase #5 $66.73   6.760%   $71.2409   $71.24   $71.25   $71.20  
  Purchase #6 $222.49   5.642%   $235.0429   $235.04   $235.05   $235.00  
  Purchase #7 $242.87   6.291%   $258.149   $258.15   $258.15   $258.10  
  7 purchase totals = $987.78       $1,060.9288   $1,060.92   $1,060.95   $1,060.80