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 $43.30   7.304%   $46.4626   $46.46   $46.45   $46.50  
  Purchase #2 $58.63   11.352%   $65.2857   $65.29   $65.30   $65.30  
  Purchase #3 $158.79   7.493%   $170.6881   $170.69   $170.70   $170.70  
  Purchase #4 $72.81   8.693%   $79.1394   $79.14   $79.15   $79.10  
  Purchase #5 $212.89   6.684%   $227.1196   $227.12   $227.10   $227.10  
  Purchase #6 $129.26   11.267%   $143.8237   $143.82   $143.80   $143.80  
  Purchase #7 $49.64   7.870%   $53.5467   $53.55   $53.55   $53.50  
  7 purchase totals = $725.32       $786.0658   $786.07   $786.05   $786.00