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 $214.83   9.225%   $234.6481   $234.65   $234.65   $234.60  
  Purchase #2 $223.64   5.543%   $236.0364   $236.04   $236.05   $236.00  
  Purchase #3 $126.38   11.403%   $140.7911   $140.79   $140.80   $140.80  
  Purchase #4 $225.80   10.122%   $248.6555   $248.66   $248.65   $248.70  
  Purchase #5 $43.81   9.503%   $47.9733   $47.97   $47.95   $48.00  
  Purchase #6 $218.75   9.852%   $240.3013   $240.30   $240.30   $240.30  
  Purchase #7 $103.32   8.170%   $111.7612   $111.76   $111.75   $111.80  
  7 purchase totals = $1,156.53       $1,260.1669   $1,260.17   $1,260.15   $1,260.20