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	$184.90	6.267%	$196.4877	$196.49	$196.50	$196.50
Purchase #2	$104.62	8.130%	$113.1256	$113.13	$113.15	$113.10
Purchase #3	$143.94	9.758%	$157.9857	$157.99	$158.00	$158.00
Purchase #4	$63.45	5.855%	$67.165	$67.17	$67.15	$67.20
Purchase #5	$167.49	11.787%	$187.232	$187.23	$187.25	$187.20
Purchase #6	$81.58	9.210%	$89.0935	$89.09	$89.10	$89.10
Purchase #7	$40.33	7.733%	$43.4487	$43.45	$43.45	$43.40
7 purchase totals =	$786.31		$854.5382	$854.55	$854.60	$854.50