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 $88.32   4.709%   $92.479   $92.48   $92.50   $92.50  
  Purchase #2 $201.70   11.410%   $224.714   $224.71   $224.70   $224.70  
  Purchase #3 $248.83   6.844%   $265.8599   $265.86   $265.85   $265.90  
  Purchase #4 $164.40   12.365%   $184.7281   $184.73   $184.75   $184.70  
  Purchase #5 $198.82   9.774%   $218.2527   $218.25   $218.25   $218.30  
  Purchase #6 $119.69   12.319%   $134.4346   $134.43   $134.45   $134.40  
  Purchase #7 $204.97   10.860%   $227.2297   $227.23   $227.25   $227.20  
  7 purchase totals = $1,226.73       $1,347.6980   $1,347.69   $1,347.75   $1,347.70