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 $41.30   5.634%   $43.6268   $43.63   $43.65   $43.60  
  Purchase #2 $144.56   5.299%   $152.2202   $152.22   $152.20   $152.20  
  Purchase #3 $157.44   12.359%   $176.898   $176.90   $176.90   $176.90  
  Purchase #4 $20.98   3.406%   $21.6946   $21.69   $21.70   $21.70  
  Purchase #5 $186.30   10.566%   $205.9845   $205.98   $206.00   $206.00  
  Purchase #6 $138.83   3.359%   $143.4933   $143.49   $143.50   $143.50  
  Purchase #7 $133.98   13.565%   $152.1544   $152.15   $152.15   $152.20  
  7 purchase totals = $823.39       $896.0718   $896.06   $896.10   $896.10