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 $110.64   3.259%   $114.2458   $114.25   $114.25   $114.20  
  Purchase #2 $162.56   8.169%   $175.8395   $175.84   $175.85   $175.80  
  Purchase #3 $205.57   7.630%   $221.255   $221.26   $221.25   $221.30  
  Purchase #4 $110.79   3.441%   $114.6023   $114.60   $114.60   $114.60  
  Purchase #5 $233.27   7.478%   $250.7139   $250.71   $250.70   $250.70  
  Purchase #6 $143.87   13.393%   $163.1385   $163.14   $163.15   $163.10  
  Purchase #7 $166.36   5.191%   $174.9957   $175.00   $175.00   $175.00  
  7 purchase totals = $1,133.06       $1,214.7907   $1,214.80   $1,214.80   $1,214.70