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	$130.58	10.238%	$143.9488	$143.95	$143.95	$143.90
Purchase #2	$52.31	4.142%	$54.4767	$54.48	$54.50	$54.50
Purchase #3	$42.82	9.443%	$46.8635	$46.86	$46.85	$46.90
Purchase #4	$67.28	3.623%	$69.7176	$69.72	$69.70	$69.70
Purchase #5	$112.35	5.578%	$118.6169	$118.62	$118.60	$118.60
Purchase #6	$45.83	7.499%	$49.2668	$49.27	$49.25	$49.30
Purchase #7	$133.60	4.638%	$139.7964	$139.80	$139.80	$139.80
7 purchase totals =	$584.77		$622.6867	$622.70	$622.65	$622.70