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 $62.25   10.277%   $68.6474   $68.65   $68.65   $68.60  
  Purchase #2 $226.68   7.671%   $244.0686   $244.07   $244.05   $244.10  
  Purchase #3 $137.41   10.562%   $151.9232   $151.92   $151.90   $151.90  
  Purchase #4 $90.32   7.354%   $96.9621   $96.96   $96.95   $97.00  
  Purchase #5 $59.79   5.825%   $63.2728   $63.27   $63.25   $63.30  
  Purchase #6 $77.48   6.692%   $82.665   $82.67   $82.65   $82.70  
  Purchase #7 $176.99   10.579%   $195.7138   $195.71   $195.70   $195.70  
  7 purchase totals = $830.92       $903.2529   $903.25   $903.15   $903.30