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 $176.69   9.158%   $192.8713   $192.87   $192.85   $192.90  
  Purchase #2 $29.96   7.398%   $32.1764   $32.18   $32.20   $32.20  
  Purchase #3 $52.86   9.549%   $57.9076   $57.91   $57.90   $57.90  
  Purchase #4 $207.66   3.836%   $215.6258   $215.63   $215.65   $215.60  
  Purchase #5 $78.68   4.462%   $82.1907   $82.19   $82.20   $82.20  
  Purchase #6 $67.82   9.294%   $74.1232   $74.12   $74.10   $74.10  
  Purchase #7 $212.27   4.565%   $221.9601   $221.96   $221.95   $222.00  
  7 purchase totals = $825.94       $876.8551   $876.86   $876.85   $876.90