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 $59.30   6.624%   $63.228   $63.23   $63.25   $63.20  
  Purchase #2 $249.80   6.242%   $265.3925   $265.39   $265.40   $265.40  
  Purchase #3 $197.93   4.440%   $206.7181   $206.72   $206.70   $206.70  
  Purchase #4 $202.56   8.310%   $219.3927   $219.39   $219.40   $219.40  
  Purchase #5 $23.29   8.638%   $25.3018   $25.30   $25.30   $25.30  
  Purchase #6 $208.40   3.223%   $215.1167   $215.12   $215.10   $215.10  
  Purchase #7 $76.37   5.264%   $80.3901   $80.39   $80.40   $80.40  
  7 purchase totals = $1,017.65       $1,075.5399   $1,075.54   $1,075.55   $1,075.50