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	$49.75	9.494%	$54.4733	$54.47	$54.45	$54.50
Purchase #2	$14.72	13.117%	$16.6508	$16.65	$16.65	$16.70
Purchase #3	$137.30	10.175%	$151.2703	$151.27	$151.25	$151.30
Purchase #4	$199.55	5.690%	$210.9044	$210.90	$210.90	$210.90
Purchase #5	$247.74	8.832%	$269.6204	$269.62	$269.60	$269.60
Purchase #6	$45.94	11.242%	$51.1046	$51.10	$51.10	$51.10
Purchase #7	$241.43	3.109%	$248.9361	$248.94	$248.95	$248.90
7 purchase totals =	$936.43		$1,002.9599	$1,002.95	$1,002.90	$1,003.00