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 $41.54   4.813%   $43.5393   $43.54   $43.55   $43.50  
  Purchase #2 $223.78   13.294%   $253.5293   $253.53   $253.55   $253.50  
  Purchase #3 $43.39   10.787%   $48.0705   $48.07   $48.05   $48.10  
  Purchase #4 $51.91   13.327%   $58.828   $58.83   $58.85   $58.80  
  Purchase #5 $71.27   12.169%   $79.9428   $79.94   $79.95   $79.90  
  Purchase #6 $235.97   10.720%   $261.266   $261.27   $261.25   $261.30  
  Purchase #7 $210.72   7.707%   $226.9602   $226.96   $226.95   $227.00  
  7 purchase totals = $878.58       $972.1361   $972.14   $972.15   $972.10