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 $86.71   10.235%   $95.5848   $95.58   $95.60   $95.60  
  Purchase #2 $136.59   5.574%   $144.2035   $144.20   $144.20   $144.20  
  Purchase #3 $183.96   12.486%   $206.9292   $206.93   $206.95   $206.90  
  Purchase #4 $55.40   5.565%   $58.483   $58.48   $58.50   $58.50  
  Purchase #5 $192.76   4.793%   $201.999   $202.00   $202.00   $202.00  
  Purchase #6 $19.50   13.719%   $22.1752   $22.18   $22.20   $22.20  
  Purchase #7 $11.27   12.523%   $12.6813   $12.68   $12.70   $12.70  
  7 purchase totals = $686.19       $742.0560   $742.05   $742.15   $742.10