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 $190.28   5.623%   $200.9794   $200.98   $201.00   $201.00  
  Purchase #2 $156.35   4.483%   $163.3592   $163.36   $163.35   $163.40  
  Purchase #3 $41.26   8.785%   $44.8847   $44.88   $44.90   $44.90  
  Purchase #4 $192.81   12.497%   $216.9055   $216.91   $216.90   $216.90  
  Purchase #5 $156.32   5.133%   $164.3439   $164.34   $164.35   $164.30  
  Purchase #6 $26.36   6.458%   $28.0623   $28.06   $28.05   $28.10  
  Purchase #7 $46.79   13.587%   $53.1474   $53.15   $53.15   $53.10  
  7 purchase totals = $810.17       $871.6824   $871.68   $871.70   $871.70