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 $161.76   7.874%   $174.497   $174.50   $174.50   $174.50  
  Purchase #2 $121.98   9.555%   $133.6352   $133.64   $133.65   $133.60  
  Purchase #3 $234.48   3.154%   $241.8755   $241.88   $241.90   $241.90  
  Purchase #4 $194.80   7.149%   $208.7263   $208.73   $208.75   $208.70  
  Purchase #5 $127.65   4.372%   $133.2309   $133.23   $133.25   $133.20  
  Purchase #6 $173.35   7.158%   $185.7584   $185.76   $185.75   $185.80  
  Purchase #7 $168.48   4.373%   $175.8476   $175.85   $175.85   $175.80  
  7 purchase totals = $1,182.50       $1,253.5709   $1,253.59   $1,253.65   $1,253.50