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 $174.83   5.360%   $184.2009   $184.20   $184.20   $184.20  
  Purchase #2 $104.78   9.136%   $114.3527   $114.35   $114.35   $114.40  
  Purchase #3 $75.39   11.702%   $84.2121   $84.21   $84.20   $84.20  
  Purchase #4 $220.68   3.135%   $227.5983   $227.60   $227.60   $227.60  
  Purchase #5 $163.26   9.228%   $178.3256   $178.33   $178.35   $178.30  
  Purchase #6 $181.86   3.451%   $188.136   $188.14   $188.15   $188.10  
  Purchase #7 $151.44   10.381%   $167.161   $167.16   $167.15   $167.20  
  7 purchase totals = $1,072.24       $1,143.9866   $1,143.99   $1,144.00   $1,144.00