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	$177.80	12.769%	$200.5033	$200.50	$200.50	$200.50
Purchase #2	$175.28	6.714%	$187.0483	$187.05	$187.05	$187.00
Purchase #3	$151.26	10.145%	$166.6053	$166.61	$166.60	$166.60
Purchase #4	$153.44	11.690%	$171.3771	$171.38	$171.40	$171.40
Purchase #5	$248.76	4.723%	$260.5089	$260.51	$260.50	$260.50
Purchase #6	$221.72	6.185%	$235.4334	$235.43	$235.45	$235.40
Purchase #7	$18.46	5.493%	$19.474	$19.47	$19.45	$19.50
7 purchase totals =	$1,146.72		$1,240.9503	$1,240.95	$1,240.95	$1,240.90