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 $236.55   10.622%   $261.6763   $261.68   $261.70   $261.70  
  Purchase #2 $43.45   9.586%   $47.6151   $47.62   $47.60   $47.60  
  Purchase #3 $243.29   13.724%   $276.6791   $276.68   $276.70   $276.70  
  Purchase #4 $82.43   13.486%   $93.5465   $93.55   $93.55   $93.50  
  Purchase #5 $236.90   9.598%   $259.6377   $259.64   $259.65   $259.60  
  Purchase #6 $219.86   8.818%   $239.2473   $239.25   $239.25   $239.20  
  Purchase #7 $249.26   8.802%   $271.1999   $271.20   $271.20   $271.20  
  7 purchase totals = $1,311.74       $1,449.6019   $1,449.62   $1,449.65   $1,449.50