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	$162.84	5.387%	$171.6122	$171.61	$171.60	$171.60
Purchase #2	$17.64	3.418%	$18.2429	$18.24	$18.25	$18.20
Purchase #3	$18.79	8.532%	$20.3932	$20.39	$20.40	$20.40
Purchase #4	$40.88	4.689%	$42.7969	$42.80	$42.80	$42.80
Purchase #5	$148.86	12.252%	$167.0983	$167.10	$167.10	$167.10
Purchase #6	$94.31	10.265%	$103.9909	$103.99	$104.00	$104.00
Purchase #7	$41.46	5.848%	$43.8846	$43.88	$43.90	$43.90
7 purchase totals =	$524.78		$568.0190	$568.01	$568.05	$568.00