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 $86.49   11.724%   $96.6301   $96.63   $96.65   $96.60  
  Purchase #2 $104.25   9.451%   $114.1027   $114.10   $114.10   $114.10  
  Purchase #3 $179.48   6.815%   $191.7116   $191.71   $191.70   $191.70  
  Purchase #4 $234.48   13.138%   $265.286   $265.29   $265.30   $265.30  
  Purchase #5 $77.77   10.838%   $86.1987   $86.20   $86.20   $86.20  
  Purchase #6 $151.87   7.643%   $163.4774   $163.48   $163.50   $163.50  
  Purchase #7 $247.58   10.707%   $274.0884   $274.09   $274.10   $274.10  
  7 purchase totals = $1,081.92       $1,191.4949   $1,191.50   $1,191.55   $1,191.50