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 $217.32   7.777%   $234.221   $234.22   $234.20   $234.20  
  Purchase #2 $234.33   3.556%   $242.6628   $242.66   $242.65   $242.70  
  Purchase #3 $118.77   3.495%   $122.921   $122.92   $122.90   $122.90  
  Purchase #4 $222.41   9.231%   $242.9407   $242.94   $242.95   $242.90  
  Purchase #5 $218.40   13.377%   $247.6154   $247.62   $247.60   $247.60  
  Purchase #6 $49.34   7.687%   $53.1328   $53.13   $53.15   $53.10  
  Purchase #7 $54.89   12.105%   $61.5344   $61.53   $61.55   $61.50  
  7 purchase totals = $1,115.46       $1,205.0281   $1,205.02   $1,205.00   $1,204.90