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 $55.82   11.696%   $62.3487   $62.35   $62.35   $62.30  
  Purchase #2 $237.58   5.515%   $250.6825   $250.68   $250.70   $250.70  
  Purchase #3 $175.55   11.433%   $195.6206   $195.62   $195.60   $195.60  
  Purchase #4 $176.25   8.749%   $191.6701   $191.67   $191.65   $191.70  
  Purchase #5 $172.30   10.439%   $190.2864   $190.29   $190.30   $190.30  
  Purchase #6 $126.55   5.273%   $133.223   $133.22   $133.20   $133.20  
  Purchase #7 $47.77   8.337%   $51.7526   $51.75   $51.75   $51.80  
  7 purchase totals = $991.82       $1,075.5839   $1,075.58   $1,075.55   $1,075.60