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 $208.86   7.278%   $224.0608   $224.06   $224.05   $224.10  
  Purchase #2 $69.57   8.530%   $75.5043   $75.50   $75.50   $75.50  
  Purchase #3 $171.42   3.315%   $177.1026   $177.10   $177.10   $177.10  
  Purchase #4 $177.95   7.276%   $190.8976   $190.90   $190.90   $190.90  
  Purchase #5 $86.83   12.448%   $97.6386   $97.64   $97.65   $97.60  
  Purchase #6 $214.61   5.490%   $226.3921   $226.39   $226.40   $226.40  
  Purchase #7 $107.34   8.454%   $116.4145   $116.41   $116.40   $116.40  
  7 purchase totals = $1,036.58       $1,108.0105   $1,108.00   $1,108.00   $1,108.00