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	$78.91	9.730%	$86.5879	$86.59	$86.60	$86.60
Purchase #2	$115.55	5.235%	$121.599	$121.60	$121.60	$121.60
Purchase #3	$104.73	7.449%	$112.5313	$112.53	$112.55	$112.50
Purchase #4	$16.38	10.330%	$18.0721	$18.07	$18.05	$18.10
Purchase #5	$97.79	7.774%	$105.3922	$105.39	$105.40	$105.40
Purchase #6	$65.28	11.460%	$72.7611	$72.76	$72.75	$72.80
Purchase #7	$43.68	8.316%	$47.3124	$47.31	$47.30	$47.30
7 purchase totals =	$522.32		$564.2560	$564.25	$564.25	$564.30