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 $214.95   6.247%   $228.3779   $228.38   $228.40   $228.40  
  Purchase #2 $53.93   11.329%   $60.0397   $60.04   $60.05   $60.00  
  Purchase #3 $159.51   12.558%   $179.5413   $179.54   $179.55   $179.50  
  Purchase #4 $241.95   6.593%   $257.9018   $257.90   $257.90   $257.90  
  Purchase #5 $147.44   11.471%   $164.3528   $164.35   $164.35   $164.40  
  Purchase #6 $146.66   10.563%   $162.1517   $162.15   $162.15   $162.20  
  Purchase #7 $63.61   6.222%   $67.5678   $67.57   $67.55   $67.60  
  7 purchase totals = $1,028.05       $1,119.9330   $1,119.93   $1,119.95   $1,120.00