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 $115.77   9.270%   $126.5019   $126.50   $126.50   $126.50  
  Purchase #2 $206.78   6.734%   $220.7046   $220.70   $220.70   $220.70  
  Purchase #3 $13.74   7.786%   $14.8098   $14.81   $14.80   $14.80  
  Purchase #4 $220.54   3.264%   $227.7384   $227.74   $227.75   $227.70  
  Purchase #5 $206.96   10.641%   $228.9826   $228.98   $229.00   $229.00  
  Purchase #6 $175.47   4.698%   $183.7136   $183.71   $183.70   $183.70  
  Purchase #7 $20.41   8.457%   $22.1361   $22.14   $22.15   $22.10  
  7 purchase totals = $959.67       $1,024.5870   $1,024.58   $1,024.60   $1,024.50