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 $240.90   8.868%   $262.263   $262.26   $262.25   $262.30  
  Purchase #2 $222.63   12.301%   $250.0157   $250.02   $250.00   $250.00  
  Purchase #3 $30.53   5.334%   $32.1585   $32.16   $32.15   $32.20  
  Purchase #4 $224.76   3.774%   $233.2424   $233.24   $233.25   $233.20  
  Purchase #5 $163.40   13.103%   $184.8103   $184.81   $184.80   $184.80  
  Purchase #6 $31.39   12.292%   $35.2485   $35.25   $35.25   $35.20  
  Purchase #7 $75.47   10.840%   $83.6509   $83.65   $83.65   $83.70  
  7 purchase totals = $989.08       $1,081.3893   $1,081.39   $1,081.35   $1,081.40