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 $61.96   12.475%   $69.6895   $69.69   $69.70   $69.70  
  Purchase #2 $228.46   11.611%   $254.9865   $254.99   $255.00   $255.00  
  Purchase #3 $60.71   6.252%   $64.5056   $64.51   $64.50   $64.50  
  Purchase #4 $190.66   11.763%   $213.0873   $213.09   $213.10   $213.10  
  Purchase #5 $103.44   11.415%   $115.2477   $115.25   $115.25   $115.20  
  Purchase #6 $168.29   7.218%   $180.4372   $180.44   $180.45   $180.40  
  Purchase #7 $161.83   5.721%   $171.0883   $171.09   $171.10   $171.10  
  7 purchase totals = $975.35       $1,069.0421   $1,069.06   $1,069.10   $1,069.00