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 $85.99   7.528%   $92.4633   $92.46   $92.45   $92.50  
  Purchase #2 $236.30   6.239%   $251.0428   $251.04   $251.05   $251.00  
  Purchase #3 $135.29   12.293%   $151.9212   $151.92   $151.90   $151.90  
  Purchase #4 $208.32   3.491%   $215.5925   $215.59   $215.60   $215.60  
  Purchase #5 $140.86   7.266%   $151.0949   $151.09   $151.10   $151.10  
  Purchase #6 $237.48   13.384%   $269.2643   $269.26   $269.25   $269.30  
  Purchase #7 $224.25   13.126%   $253.6851   $253.69   $253.70   $253.70  
  7 purchase totals = $1,268.49       $1,385.0641   $1,385.05   $1,385.05   $1,385.10