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	$219.86	4.192%	$229.0765	$229.08	$229.10	$229.10
Purchase #2	$148.51	3.600%	$153.8564	$153.86	$153.85	$153.90
Purchase #3	$100.36	3.195%	$103.5665	$103.57	$103.55	$103.60
Purchase #4	$137.87	4.156%	$143.5999	$143.60	$143.60	$143.60
Purchase #5	$179.43	10.802%	$198.812	$198.81	$198.80	$198.80
Purchase #6	$43.91	8.104%	$47.4685	$47.47	$47.45	$47.50
Purchase #7	$127.97	9.388%	$139.9838	$139.98	$140.00	$140.00
7 purchase totals =	$957.91		$1,016.3636	$1,016.37	$1,016.35	$1,016.50