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	$102.66	13.352%	$116.3672	$116.37	$116.35	$116.40
Purchase #2	$221.33	3.522%	$229.1252	$229.13	$229.15	$229.10
Purchase #3	$250.67	9.255%	$273.8695	$273.87	$273.85	$273.90
Purchase #4	$114.70	7.647%	$123.4711	$123.47	$123.45	$123.50
Purchase #5	$10.98	7.841%	$11.8409	$11.84	$11.85	$11.80
Purchase #6	$124.26	13.530%	$141.0724	$141.07	$141.05	$141.10
Purchase #7	$143.83	3.241%	$148.4915	$148.49	$148.50	$148.50
7 purchase totals =	$968.43		$1,044.2378	$1,044.24	$1,044.20	$1,044.30