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 $115.59   8.696%   $125.6417   $125.64   $125.65   $125.60  
  Purchase #2 $81.91   12.859%   $92.4428   $92.44   $92.45   $92.40  
  Purchase #3 $198.25   9.484%   $217.052   $217.05   $217.05   $217.10  
  Purchase #4 $37.26   4.742%   $39.0269   $39.03   $39.05   $39.00  
  Purchase #5 $227.81   4.256%   $237.5056   $237.51   $237.50   $237.50  
  Purchase #6 $235.95   13.127%   $266.9232   $266.92   $266.90   $266.90  
  Purchase #7 $84.46   13.716%   $96.0445   $96.04   $96.05   $96.00  
  7 purchase totals = $981.23       $1,074.6367   $1,074.63   $1,074.65   $1,074.50