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 $107.69   6.753%   $114.9623   $114.96   $114.95   $115.00  
  Purchase #2 $222.81   4.238%   $232.2527   $232.25   $232.25   $232.30  
  Purchase #3 $95.86   13.563%   $108.8615   $108.86   $108.85   $108.90  
  Purchase #4 $11.49   13.423%   $13.0323   $13.03   $13.05   $13.00  
  Purchase #5 $75.68   13.635%   $85.999   $86.00   $86.00   $86.00  
  Purchase #6 $84.44   3.814%   $87.6605   $87.66   $87.65   $87.70  
  Purchase #7 $161.85   11.583%   $180.5971   $180.60   $180.60   $180.60  
  7 purchase totals = $759.82       $823.3654   $823.36   $823.35   $823.50