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 $219.90   11.854%   $245.9669   $245.97   $245.95   $246.00  
  Purchase #2 $181.94   13.274%   $206.0907   $206.09   $206.10   $206.10  
  Purchase #3 $112.62   12.745%   $126.9734   $126.97   $126.95   $127.00  
  Purchase #4 $103.70   4.626%   $108.4972   $108.50   $108.50   $108.50  
  Purchase #5 $14.76   8.720%   $16.0471   $16.05   $16.05   $16.00  
  Purchase #6 $151.75   3.366%   $156.8579   $156.86   $156.85   $156.90  
  Purchase #7 $236.94   10.792%   $262.5106   $262.51   $262.50   $262.50  
  7 purchase totals = $1,021.61       $1,122.9438   $1,122.95   $1,122.90   $1,123.00