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 $107.53   6.254%   $114.2549   $114.25   $114.25   $114.30  
  Purchase #2 $142.96   11.115%   $158.85   $158.85   $158.85   $158.90  
  Purchase #3 $226.95   6.629%   $241.9945   $241.99   $242.00   $242.00  
  Purchase #4 $241.89   13.190%   $273.7953   $273.80   $273.80   $273.80  
  Purchase #5 $163.65   11.361%   $182.2423   $182.24   $182.25   $182.20  
  Purchase #6 $121.90   10.337%   $134.5008   $134.50   $134.50   $134.50  
  Purchase #7 $62.26   5.235%   $65.5193   $65.52   $65.50   $65.50  
  7 purchase totals = $1,067.14       $1,171.1571   $1,171.15   $1,171.15   $1,171.20