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 $53.90   9.512%   $59.027   $59.03   $59.05   $59.00  
  Purchase #2 $84.38   13.331%   $95.6287   $95.63   $95.65   $95.60  
  Purchase #3 $189.51   6.461%   $201.7542   $201.75   $201.75   $201.80  
  Purchase #4 $73.88   6.262%   $78.5064   $78.51   $78.50   $78.50  
  Purchase #5 $175.42   11.219%   $195.1004   $195.10   $195.10   $195.10  
  Purchase #6 $193.39   10.773%   $214.2239   $214.22   $214.20   $214.20  
  Purchase #7 $109.60   4.835%   $114.8992   $114.90   $114.90   $114.90  
  7 purchase totals = $880.08       $959.1398   $959.14   $959.15   $959.10