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	$105.84	5.401%	$111.5564	$111.56	$111.55	$111.60
Purchase #2	$120.89	9.243%	$132.0639	$132.06	$132.05	$132.10
Purchase #3	$110.26	3.633%	$114.2657	$114.27	$114.25	$114.30
Purchase #4	$84.58	4.404%	$88.3049	$88.30	$88.30	$88.30
Purchase #5	$49.55	11.305%	$55.1516	$55.15	$55.15	$55.20
Purchase #6	$208.66	10.256%	$230.0602	$230.06	$230.05	$230.10
Purchase #7	$106.58	5.222%	$112.1456	$112.15	$112.15	$112.10
7 purchase totals =	$786.36		$843.5483	$843.55	$843.50	$843.70