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 $161.32   13.171%   $182.5675   $182.57   $182.55   $182.60  
  Purchase #2 $142.48   12.716%   $160.5978   $160.60   $160.60   $160.60  
  Purchase #3 $44.81   4.193%   $46.6889   $46.69   $46.70   $46.70  
  Purchase #4 $102.61   13.314%   $116.2715   $116.27   $116.25   $116.30  
  Purchase #5 $166.71   9.486%   $182.5241   $182.52   $182.50   $182.50  
  Purchase #6 $69.44   3.258%   $71.7024   $71.70   $71.70   $71.70  
  Purchase #7 $107.60   7.315%   $115.4709   $115.47   $115.45   $115.50  
  7 purchase totals = $794.97       $875.8231   $875.82   $875.75   $875.90