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	$208.94	10.671%	$231.236	$231.24	$231.25	$231.20
Purchase #2	$199.49	13.513%	$226.4471	$226.45	$226.45	$226.40
Purchase #3	$9.53	6.604%	$10.1594	$10.16	$10.15	$10.20
Purchase #4	$107.91	3.558%	$111.7494	$111.75	$111.75	$111.70
Purchase #5	$137.34	9.661%	$150.6084	$150.61	$150.60	$150.60
Purchase #6	$5.95	4.640%	$6.2261	$6.23	$6.25	$6.20
Purchase #7	$39.75	10.471%	$43.9122	$43.91	$43.90	$43.90
7 purchase totals =	$708.91		$780.3386	$780.35	$780.35	$780.20