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 $66.70   3.817%   $69.2459   $69.25   $69.25   $69.20  
  Purchase #2 $217.44   9.358%   $237.788   $237.79   $237.80   $237.80  
  Purchase #3 $161.33   5.297%   $169.8757   $169.88   $169.90   $169.90  
  Purchase #4 $177.38   11.469%   $197.7237   $197.72   $197.70   $197.70  
  Purchase #5 $144.37   5.196%   $151.8715   $151.87   $151.85   $151.90  
  Purchase #6 $57.68   13.397%   $65.4074   $65.41   $65.40   $65.40  
  Purchase #7 $46.32   13.704%   $52.6677   $52.67   $52.65   $52.70  
  7 purchase totals = $871.22       $944.5799   $944.59   $944.55   $944.60