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	$137.97	11.317%	$153.5841	$153.58	$153.60	$153.60
Purchase #2	$196.41	8.602%	$213.3052	$213.31	$213.30	$213.30
Purchase #3	$122.47	3.498%	$126.754	$126.75	$126.75	$126.80
Purchase #4	$126.35	10.149%	$139.1733	$139.17	$139.15	$139.20
Purchase #5	$103.42	7.855%	$111.5436	$111.54	$111.55	$111.50
Purchase #6	$214.82	7.258%	$230.4116	$230.41	$230.40	$230.40
Purchase #7	$109.74	6.415%	$116.7798	$116.78	$116.80	$116.80
7 purchase totals =	$1,011.18		$1,091.5516	$1,091.54	$1,091.55	$1,091.60