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 $214.83   3.627%   $222.6219   $222.62   $222.60   $222.60  
  Purchase #2 $93.77   11.144%   $104.2197   $104.22   $104.20   $104.20  
  Purchase #3 $224.28   7.617%   $241.3634   $241.36   $241.35   $241.40  
  Purchase #4 $250.79   9.569%   $274.7881   $274.79   $274.80   $274.80  
  Purchase #5 $211.85   9.830%   $232.6749   $232.67   $232.65   $232.70  
  Purchase #6 $104.75   3.558%   $108.477   $108.48   $108.50   $108.50  
  Purchase #7 $74.63   11.430%   $83.1602   $83.16   $83.15   $83.20  
  7 purchase totals = $1,174.90       $1,267.3052   $1,267.30   $1,267.25   $1,267.40