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 $182.54   13.378%   $206.9602   $206.96   $206.95   $207.00  
  Purchase #2 $242.42   8.104%   $262.0657   $262.07   $262.05   $262.10  
  Purchase #3 $215.50   13.720%   $245.0666   $245.07   $245.05   $245.10  
  Purchase #4 $163.53   3.772%   $169.6984   $169.70   $169.70   $169.70  
  Purchase #5 $66.98   4.645%   $70.0912   $70.09   $70.10   $70.10  
  Purchase #6 $201.64   3.387%   $208.4695   $208.47   $208.45   $208.50  
  Purchase #7 $235.93   4.538%   $246.6365   $246.64   $246.65   $246.60  
  7 purchase totals = $1,308.54       $1,408.9881   $1,409.00   $1,408.95   $1,409.10