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	$159.58	8.657%	$173.3948	$173.39	$173.40	$173.40
Purchase #2	$164.38	4.685%	$172.0812	$172.08	$172.10	$172.10
Purchase #3	$162.81	8.856%	$177.2285	$177.23	$177.25	$177.20
Purchase #4	$96.43	9.521%	$105.6111	$105.61	$105.60	$105.60
Purchase #5	$169.75	6.570%	$180.9026	$180.90	$180.90	$180.90
Purchase #6	$126.32	13.226%	$143.0271	$143.03	$143.05	$143.00
Purchase #7	$153.49	3.628%	$159.0586	$159.06	$159.05	$159.10
7 purchase totals =	$1,032.76		$1,111.3039	$1,111.30	$1,111.35	$1,111.30