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 $117.96   5.626%   $124.5964   $124.60   $124.60   $124.60  
  Purchase #2 $95.74   10.542%   $105.8329   $105.83   $105.85   $105.80  
  Purchase #3 $250.48   7.126%   $268.3292   $268.33   $268.35   $268.30  
  Purchase #4 $244.94   8.517%   $265.8015   $265.80   $265.80   $265.80  
  Purchase #5 $81.51   5.727%   $86.1781   $86.18   $86.20   $86.20  
  Purchase #6 $151.89   3.674%   $157.4704   $157.47   $157.45   $157.50  
  Purchase #7 $186.74   7.149%   $200.09   $200.09   $200.10   $200.10  
  7 purchase totals = $1,129.26       $1,208.2985   $1,208.30   $1,208.35   $1,208.30