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 $55.68   10.687%   $61.6305   $61.63   $61.65   $61.60  
  Purchase #2 $67.85   4.796%   $71.1041   $71.10   $71.10   $71.10  
  Purchase #3 $111.48   8.185%   $120.6046   $120.60   $120.60   $120.60  
  Purchase #4 $239.70   5.268%   $252.3274   $252.33   $252.35   $252.30  
  Purchase #5 $109.67   10.535%   $121.2237   $121.22   $121.20   $121.20  
  Purchase #6 $236.41   4.796%   $247.7482   $247.75   $247.75   $247.70  
  Purchase #7 $214.28   6.182%   $227.5268   $227.53   $227.55   $227.50  
  7 purchase totals = $1,035.07       $1,102.1653   $1,102.16   $1,102.20   $1,102.00