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 $194.43   7.115%   $208.2637   $208.26   $208.25   $208.30  
  Purchase #2 $177.89   3.185%   $183.5558   $183.56   $183.55   $183.60  
  Purchase #3 $186.69   10.342%   $205.9975   $206.00   $206.00   $206.00  
  Purchase #4 $180.62   11.858%   $202.0379   $202.04   $202.05   $202.00  
  Purchase #5 $80.89   5.862%   $85.6318   $85.63   $85.65   $85.60  
  Purchase #6 $168.32   10.693%   $186.3185   $186.32   $186.30   $186.30  
  Purchase #7 $152.32   7.141%   $163.1972   $163.20   $163.20   $163.20  
  7 purchase totals = $1,141.16       $1,235.0024   $1,235.01   $1,235.00   $1,235.00