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	$94.46	6.732%	$100.819	$100.82	$100.80	$100.80
Purchase #2	$164.81	10.396%	$181.9436	$181.94	$181.95	$181.90
Purchase #3	$71.76	8.383%	$77.7756	$77.78	$77.80	$77.80
Purchase #4	$101.32	10.411%	$111.8684	$111.87	$111.85	$111.90
Purchase #5	$248.44	7.294%	$266.5612	$266.56	$266.55	$266.60
Purchase #6	$231.72	9.786%	$254.3961	$254.40	$254.40	$254.40
Purchase #7	$107.51	5.729%	$113.6692	$113.67	$113.65	$113.70
7 purchase totals =	$1,020.02		$1,107.0331	$1,107.04	$1,107.00	$1,107.10