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 $64.38   7.580%   $69.26   $69.26   $69.25   $69.30  
  Purchase #2 $207.62   11.244%   $230.9648   $230.96   $230.95   $231.00  
  Purchase #3 $200.67   12.757%   $226.2695   $226.27   $226.25   $226.30  
  Purchase #4 $164.68   7.408%   $176.8795   $176.88   $176.90   $176.90  
  Purchase #5 $220.72   6.255%   $234.526   $234.53   $234.55   $234.50  
  Purchase #6 $15.63   12.848%   $17.6381   $17.64   $17.65   $17.60  
  Purchase #7 $119.28   10.250%   $131.5062   $131.51   $131.50   $131.50  
  7 purchase totals = $992.98       $1,087.0441   $1,087.05   $1,087.05   $1,087.10