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 $67.40   3.232%   $69.5784   $69.58   $69.60   $69.60  
  Purchase #2 $112.29   5.662%   $118.6479   $118.65   $118.65   $118.60  
  Purchase #3 $214.79   5.682%   $226.9944   $226.99   $227.00   $227.00  
  Purchase #4 $156.47   12.209%   $175.5734   $175.57   $175.55   $175.60  
  Purchase #5 $194.60   3.159%   $200.7474   $200.75   $200.75   $200.70  
  Purchase #6 $100.53   4.116%   $104.6678   $104.67   $104.65   $104.70  
  Purchase #7 $208.62   13.203%   $236.1641   $236.16   $236.15   $236.20  
  7 purchase totals = $1,054.70       $1,132.3734   $1,132.37   $1,132.35   $1,132.40