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 $195.95   10.764%   $217.0421   $217.04   $217.05   $217.00  
  Purchase #2 $222.38   13.435%   $252.2568   $252.26   $252.25   $252.30  
  Purchase #3 $76.80   10.611%   $84.9492   $84.95   $84.95   $84.90  
  Purchase #4 $151.74   3.621%   $157.2345   $157.23   $157.25   $157.20  
  Purchase #5 $154.63   12.523%   $173.9943   $173.99   $174.00   $174.00  
  Purchase #6 $92.33   4.299%   $96.2993   $96.30   $96.30   $96.30  
  Purchase #7 $152.26   4.441%   $159.0219   $159.02   $159.00   $159.00  
  7 purchase totals = $1,046.09       $1,140.7981   $1,140.79   $1,140.80   $1,140.70