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 $192.98   7.831%   $208.0923   $208.09   $208.10   $208.10  
  Purchase #2 $101.62   12.174%   $113.9912   $113.99   $114.00   $114.00  
  Purchase #3 $247.95   10.448%   $273.8558   $273.86   $273.85   $273.90  
  Purchase #4 $164.31   7.566%   $176.7417   $176.74   $176.75   $176.70  
  Purchase #5 $185.88   6.696%   $198.3265   $198.33   $198.35   $198.30  
  Purchase #6 $156.95   5.373%   $165.3829   $165.38   $165.40   $165.40  
  Purchase #7 $23.26   6.135%   $24.687   $24.69   $24.70   $24.70  
  7 purchase totals = $1,072.95       $1,161.0774   $1,161.08   $1,161.15   $1,161.10