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 $40.76   7.826%   $43.9499   $43.95   $43.95   $43.90  
  Purchase #2 $205.86   4.161%   $214.4258   $214.43   $214.45   $214.40  
  Purchase #3 $93.65   5.203%   $98.5226   $98.52   $98.50   $98.50  
  Purchase #4 $106.45   10.621%   $117.7561   $117.76   $117.75   $117.80  
  Purchase #5 $199.93   5.837%   $211.5999   $211.60   $211.60   $211.60  
  Purchase #6 $154.70   12.617%   $174.2185   $174.22   $174.20   $174.20  
  Purchase #7 $95.87   6.558%   $102.1572   $102.16   $102.15   $102.20  
  7 purchase totals = $897.22       $962.6300   $962.64   $962.60   $962.60