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	$60.51	7.302%	$64.9284	$64.93	$64.95	$64.90
Purchase #2	$52.68	12.189%	$59.1012	$59.10	$59.10	$59.10
Purchase #3	$60.76	6.483%	$64.6991	$64.70	$64.70	$64.70
Purchase #4	$250.34	10.492%	$276.6057	$276.61	$276.60	$276.60
Purchase #5	$28.42	4.711%	$29.7589	$29.76	$29.75	$29.80
Purchase #6	$81.95	9.575%	$89.7967	$89.80	$89.80	$89.80
Purchase #7	$41.95	10.746%	$46.4579	$46.46	$46.45	$46.50
7 purchase totals =	$576.61		$631.3479	$631.36	$631.35	$631.40