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 $103.83   9.796%   $114.0012   $114.00   $114.00   $114.00  
  Purchase #2 $103.55   12.678%   $116.6781   $116.68   $116.70   $116.70  
  Purchase #3 $65.68   7.353%   $70.5095   $70.51   $70.50   $70.50  
  Purchase #4 $39.49   4.189%   $41.1442   $41.14   $41.15   $41.10  
  Purchase #5 $224.56   5.125%   $236.0687   $236.07   $236.05   $236.10  
  Purchase #6 $54.35   4.292%   $56.6827   $56.68   $56.70   $56.70  
  Purchase #7 $204.29   8.376%   $221.4013   $221.40   $221.40   $221.40  
  7 purchase totals = $795.75       $856.4857   $856.48   $856.50   $856.50