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	$130.67	13.782%	$148.6789	$148.68	$148.70	$148.70
Purchase #2	$126.38	10.522%	$139.6777	$139.68	$139.70	$139.70
Purchase #3	$112.82	10.370%	$124.5194	$124.52	$124.50	$124.50
Purchase #4	$95.47	4.272%	$99.5485	$99.55	$99.55	$99.50
Purchase #5	$25.71	13.177%	$29.0978	$29.10	$29.10	$29.10
Purchase #6	$167.25	7.523%	$179.8322	$179.83	$179.85	$179.80
Purchase #7	$40.45	3.719%	$41.9543	$41.95	$41.95	$42.00
7 purchase totals =	$698.75		$763.3088	$763.31	$763.35	$763.30