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	$57.79	13.208%	$65.4229	$65.42	$65.40	$65.40
Purchase #2	$190.93	8.812%	$207.7548	$207.75	$207.75	$207.80
Purchase #3	$96.26	4.290%	$100.3896	$100.39	$100.40	$100.40
Purchase #4	$205.59	6.192%	$218.3201	$218.32	$218.30	$218.30
Purchase #5	$115.78	12.729%	$130.5176	$130.52	$130.50	$130.50
Purchase #6	$155.88	13.336%	$176.6682	$176.67	$176.65	$176.70
Purchase #7	$129.77	13.147%	$146.8309	$146.83	$146.85	$146.80
7 purchase totals =	$952.00		$1,045.9041	$1,045.90	$1,045.85	$1,045.90