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	$102.35	8.732%	$111.2872	$111.29	$111.30	$111.30
Purchase #2	$76.30	3.357%	$78.8614	$78.86	$78.85	$78.90
Purchase #3	$183.60	10.739%	$203.3168	$203.32	$203.30	$203.30
Purchase #4	$165.27	7.688%	$177.976	$177.98	$178.00	$178.00
Purchase #5	$222.69	4.797%	$233.3724	$233.37	$233.35	$233.40
Purchase #6	$199.75	3.275%	$206.2918	$206.29	$206.30	$206.30
Purchase #7	$19.42	13.783%	$22.0967	$22.10	$22.10	$22.10
7 purchase totals =	$969.38		$1,033.2023	$1,033.21	$1,033.20	$1,033.30