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	$53.94	4.433%	$56.3312	$56.33	$56.35	$56.30
Purchase #2	$227.93	10.493%	$251.8467	$251.85	$251.85	$251.80
Purchase #3	$209.95	9.768%	$230.4579	$230.46	$230.45	$230.50
Purchase #4	$148.72	9.196%	$162.3963	$162.40	$162.40	$162.40
Purchase #5	$35.74	13.408%	$40.532	$40.53	$40.55	$40.50
Purchase #6	$37.47	5.455%	$39.514	$39.51	$39.50	$39.50
Purchase #7	$212.26	11.478%	$236.6232	$236.62	$236.60	$236.60
7 purchase totals =	$926.01		$1,017.7013	$1,017.70	$1,017.70	$1,017.60