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 $13.69   6.313%   $14.5542   $14.55   $14.55   $14.60  
  Purchase #2 $176.75   3.116%   $182.2575   $182.26   $182.25   $182.30  
  Purchase #3 $130.56   12.180%   $146.4622   $146.46   $146.45   $146.50  
  Purchase #4 $109.94   12.765%   $123.9738   $123.97   $123.95   $124.00  
  Purchase #5 $42.70   8.502%   $46.3304   $46.33   $46.35   $46.30  
  Purchase #6 $248.31   10.125%   $273.4514   $273.45   $273.45   $273.50  
  Purchase #7 $201.57   12.799%   $227.3689   $227.37   $227.35   $227.40  
  7 purchase totals = $923.52       $1,014.3984   $1,014.39   $1,014.35   $1,014.60