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	$239.25	10.819%	$265.1345	$265.13	$265.15	$265.10
Purchase #2	$200.26	12.654%	$225.6009	$225.60	$225.60	$225.60
Purchase #3	$200.58	8.363%	$217.3545	$217.35	$217.35	$217.40
Purchase #4	$243.87	12.509%	$274.3757	$274.38	$274.40	$274.40
Purchase #5	$165.65	3.778%	$171.9083	$171.91	$171.90	$171.90
Purchase #6	$151.77	4.307%	$158.3067	$158.31	$158.30	$158.30
Purchase #7	$129.45	13.788%	$147.2986	$147.30	$147.30	$147.30
7 purchase totals =	$1,330.83		$1,459.9792	$1,459.98	$1,460.00	$1,460.00