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 $213.25   5.760%   $225.5332   $225.53   $225.55   $225.50  
  Purchase #2 $25.64   5.328%   $27.0061   $27.01   $27.00   $27.00  
  Purchase #3 $44.70   4.583%   $46.7486   $46.75   $46.75   $46.70  
  Purchase #4 $171.95   12.276%   $193.0586   $193.06   $193.05   $193.10  
  Purchase #5 $220.84   12.147%   $247.6654   $247.67   $247.65   $247.70  
  Purchase #6 $163.33   7.116%   $174.9526   $174.95   $174.95   $175.00  
  Purchase #7 $236.70   5.184%   $248.9705   $248.97   $248.95   $249.00  
  7 purchase totals = $1,076.41       $1,163.9350   $1,163.94   $1,163.90   $1,164.00