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 $197.75   5.543%   $208.7113   $208.71   $208.70   $208.70  
  Purchase #2 $48.73   9.589%   $53.4027   $53.40   $53.40   $53.40  
  Purchase #3 $162.56   3.469%   $168.1992   $168.20   $168.20   $168.20  
  Purchase #4 $180.98   10.379%   $199.7639   $199.76   $199.75   $199.80  
  Purchase #5 $186.40   4.111%   $194.0629   $194.06   $194.05   $194.10  
  Purchase #6 $64.51   13.408%   $73.1595   $73.16   $73.15   $73.20  
  Purchase #7 $156.68   8.592%   $170.1419   $170.14   $170.15   $170.10  
  7 purchase totals = $997.61       $1,067.4414   $1,067.43   $1,067.40   $1,067.50