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	$191.97	6.536%	$204.5172	$204.52	$204.50	$204.50
Purchase #2	$59.31	9.475%	$64.9296	$64.93	$64.95	$64.90
Purchase #3	$51.75	5.416%	$54.5528	$54.55	$54.55	$54.60
Purchase #4	$185.69	10.619%	$205.4084	$205.41	$205.40	$205.40
Purchase #5	$19.99	7.300%	$21.4493	$21.45	$21.45	$21.40
Purchase #6	$38.76	4.217%	$40.3945	$40.39	$40.40	$40.40
Purchase #7	$238.75	8.242%	$258.4278	$258.43	$258.45	$258.40
7 purchase totals =	$786.22		$849.6796	$849.68	$849.70	$849.60