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 $198.87   7.823%   $214.4276   $214.43   $214.45   $214.40  
  Purchase #2 $227.39   9.558%   $249.1239   $249.12   $249.10   $249.10  
  Purchase #3 $56.37   6.777%   $60.1902   $60.19   $60.20   $60.20  
  Purchase #4 $44.28   11.136%   $49.211   $49.21   $49.20   $49.20  
  Purchase #5 $90.51   5.517%   $95.5034   $95.50   $95.50   $95.50  
  Purchase #6 $248.25   7.172%   $266.0545   $266.05   $266.05   $266.10  
  Purchase #7 $78.87   7.712%   $84.9525   $84.95   $84.95   $85.00  
  7 purchase totals = $944.54       $1,019.4631   $1,019.45   $1,019.45   $1,019.50