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 $199.41   7.347%   $214.0607   $214.06   $214.05   $214.10  
  Purchase #2 $68.63   4.841%   $71.9524   $71.95   $71.95   $72.00  
  Purchase #3 $244.55   9.432%   $267.616   $267.62   $267.60   $267.60  
  Purchase #4 $75.25   3.524%   $77.9018   $77.90   $77.90   $77.90  
  Purchase #5 $131.71   9.772%   $144.5807   $144.58   $144.60   $144.60  
  Purchase #6 $76.56   13.619%   $86.9867   $86.99   $87.00   $87.00  
  Purchase #7 $171.31   12.871%   $193.3593   $193.36   $193.35   $193.40  
  7 purchase totals = $967.42       $1,056.4576   $1,056.46   $1,056.45   $1,056.60