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 $68.28   12.377%   $76.731   $76.73   $76.75   $76.70  
  Purchase #2 $94.96   12.757%   $107.074   $107.07   $107.05   $107.10  
  Purchase #3 $157.96   3.669%   $163.7556   $163.76   $163.75   $163.80  
  Purchase #4 $205.68   3.738%   $213.3683   $213.37   $213.35   $213.40  
  Purchase #5 $185.48   7.118%   $198.6825   $198.68   $198.70   $198.70  
  Purchase #6 $231.25   11.799%   $258.5352   $258.54   $258.55   $258.50  
  Purchase #7 $72.33   5.295%   $76.1599   $76.16   $76.15   $76.20  
  7 purchase totals = $1,015.94       $1,094.3065   $1,094.31   $1,094.30   $1,094.40