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 $59.45   5.542%   $62.7447   $62.74   $62.75   $62.70  
  Purchase #2 $14.37   10.371%   $15.8603   $15.86   $15.85   $15.90  
  Purchase #3 $178.91   4.122%   $186.2847   $186.28   $186.30   $186.30  
  Purchase #4 $126.78   10.467%   $140.0501   $140.05   $140.05   $140.10  
  Purchase #5 $250.43   3.246%   $258.559   $258.56   $258.55   $258.60  
  Purchase #6 $16.27   4.539%   $17.0085   $17.01   $17.00   $17.00  
  Purchase #7 $119.80   11.225%   $133.2476   $133.25   $133.25   $133.20  
  7 purchase totals = $766.01       $813.7549   $813.75   $813.75   $813.80