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	$161.43	9.310%	$176.4591	$176.46	$176.45	$176.50
Purchase #2	$208.41	6.647%	$222.263	$222.26	$222.25	$222.30
Purchase #3	$197.84	8.703%	$215.058	$215.06	$215.05	$215.10
Purchase #4	$132.56	3.660%	$137.4117	$137.41	$137.40	$137.40
Purchase #5	$103.54	7.339%	$111.1388	$111.14	$111.15	$111.10
Purchase #6	$70.91	9.686%	$77.7783	$77.78	$77.80	$77.80
Purchase #7	$26.45	10.243%	$29.1593	$29.16	$29.15	$29.20
7 purchase totals =	$901.14		$969.2682	$969.27	$969.25	$969.40