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	$165.60	8.306%	$179.3547	$179.35	$179.35	$179.40
Purchase #2	$8.62	10.609%	$9.5345	$9.53	$9.55	$9.50
Purchase #3	$40.30	10.298%	$44.4501	$44.45	$44.45	$44.50
Purchase #4	$158.44	8.203%	$171.4368	$171.44	$171.45	$171.40
Purchase #5	$133.27	8.120%	$144.0915	$144.09	$144.10	$144.10
Purchase #6	$100.30	11.420%	$111.7543	$111.75	$111.75	$111.80
Purchase #7	$89.64	11.640%	$100.0741	$100.07	$100.05	$100.10
7 purchase totals =	$696.17		$760.6960	$760.68	$760.70	$760.80