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	$43.78	6.620%	$46.6782	$46.68	$46.70	$46.70
Purchase #2	$226.71	10.194%	$249.8208	$249.82	$249.80	$249.80
Purchase #3	$61.36	6.447%	$65.3159	$65.32	$65.30	$65.30
Purchase #4	$172.26	5.125%	$181.0883	$181.09	$181.10	$181.10
Purchase #5	$188.45	4.376%	$196.6966	$196.70	$196.70	$196.70
Purchase #6	$238.38	8.255%	$258.0583	$258.06	$258.05	$258.10
Purchase #7	$136.47	7.257%	$146.3736	$146.37	$146.35	$146.40
7 purchase totals =	$1,067.41		$1,144.0317	$1,144.04	$1,144.00	$1,144.10