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	$219.68	10.422%	$242.575	$242.58	$242.60	$242.60
Purchase #2	$40.54	4.599%	$42.4044	$42.40	$42.40	$42.40
Purchase #3	$240.86	10.580%	$266.343	$266.34	$266.35	$266.30
Purchase #4	$59.69	10.758%	$66.1115	$66.11	$66.10	$66.10
Purchase #5	$238.76	8.705%	$259.5441	$259.54	$259.55	$259.50
Purchase #6	$248.91	3.135%	$256.7133	$256.71	$256.70	$256.70
Purchase #7	$170.84	11.388%	$190.2953	$190.30	$190.30	$190.30
7 purchase totals =	$1,219.28		$1,323.9866	$1,323.98	$1,324.00	$1,323.90