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	$106.71	4.461%	$111.4703	$111.47	$111.45	$111.50
Purchase #2	$174.46	9.601%	$191.2099	$191.21	$191.20	$191.20
Purchase #3	$12.59	13.317%	$14.2666	$14.27	$14.25	$14.30
Purchase #4	$114.33	3.711%	$118.5728	$118.57	$118.55	$118.60
Purchase #5	$181.86	4.715%	$190.4347	$190.43	$190.45	$190.40
Purchase #6	$182.57	6.636%	$194.6853	$194.69	$194.70	$194.70
Purchase #7	$227.42	10.807%	$251.9973	$252.00	$252.00	$252.00
7 purchase totals =	$999.94		$1,072.6369	$1,072.64	$1,072.60	$1,072.70