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	$107.25	4.129%	$111.6784	$111.68	$111.70	$111.70
Purchase #2	$88.77	8.808%	$96.5889	$96.59	$96.60	$96.60
Purchase #3	$62.38	4.630%	$65.2682	$65.27	$65.25	$65.30
Purchase #4	$248.81	13.121%	$281.4564	$281.46	$281.45	$281.50
Purchase #5	$132.25	9.694%	$145.0703	$145.07	$145.05	$145.10
Purchase #6	$209.36	8.643%	$227.455	$227.46	$227.45	$227.50
Purchase #7	$96.89	9.819%	$106.4036	$106.40	$106.40	$106.40
7 purchase totals =	$945.71		$1,033.9208	$1,033.93	$1,033.90	$1,034.10