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 $41.50   7.334%   $44.5436   $44.54   $44.55   $44.50  
  Purchase #2 $233.52   6.470%   $248.6287   $248.63   $248.65   $248.60  
  Purchase #3 $183.34   13.813%   $208.6648   $208.66   $208.65   $208.70  
  Purchase #4 $248.34   13.506%   $281.8808   $281.88   $281.90   $281.90  
  Purchase #5 $243.90   10.759%   $270.1412   $270.14   $270.15   $270.10  
  Purchase #6 $115.96   5.769%   $122.6497   $122.65   $122.65   $122.60  
  Purchase #7 $76.60   10.455%   $84.6085   $84.61   $84.60   $84.60  
  7 purchase totals = $1,143.16       $1,261.1173   $1,261.11   $1,261.15   $1,261.00