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	$153.28	12.592%	$172.581	$172.58	$172.60	$172.60
Purchase #2	$160.42	8.209%	$173.5889	$173.59	$173.60	$173.60
Purchase #3	$188.60	8.836%	$205.2647	$205.26	$205.25	$205.30
Purchase #4	$146.90	9.150%	$160.3414	$160.34	$160.35	$160.30
Purchase #5	$213.87	10.392%	$236.0954	$236.10	$236.10	$236.10
Purchase #6	$74.88	4.498%	$78.2481	$78.25	$78.25	$78.20
Purchase #7	$130.30	4.682%	$136.4006	$136.40	$136.40	$136.40
7 purchase totals =	$1,068.25		$1,162.5201	$1,162.52	$1,162.55	$1,162.50