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	$66.83	5.330%	$70.392	$70.39	$70.40	$70.40
Purchase #2	$112.71	4.371%	$117.6366	$117.64	$117.65	$117.60
Purchase #3	$202.57	9.793%	$222.4077	$222.41	$222.40	$222.40
Purchase #4	$57.39	6.200%	$60.9482	$60.95	$60.95	$60.90
Purchase #5	$45.82	12.175%	$51.3986	$51.40	$51.40	$51.40
Purchase #6	$242.88	9.724%	$266.4977	$266.50	$266.50	$266.50
Purchase #7	$229.35	12.594%	$258.2343	$258.23	$258.25	$258.20
7 purchase totals =	$957.55		$1,047.5151	$1,047.52	$1,047.55	$1,047.40