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	$114.96	3.871%	$119.4101	$119.41	$119.40	$119.40
Purchase #2	$107.45	3.840%	$111.5761	$111.58	$111.60	$111.60
Purchase #3	$20.39	12.521%	$22.943	$22.94	$22.95	$22.90
Purchase #4	$210.58	10.866%	$233.4616	$233.46	$233.45	$233.50
Purchase #5	$71.65	13.382%	$81.2382	$81.24	$81.25	$81.20
Purchase #6	$45.68	10.542%	$50.4956	$50.50	$50.50	$50.50
Purchase #7	$136.41	4.228%	$142.1774	$142.18	$142.20	$142.20
7 purchase totals =	$707.12		$761.3020	$761.31	$761.35	$761.30