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	$49.96	8.247%	$54.0802	$54.08	$54.10	$54.10
Purchase #2	$126.85	13.619%	$144.1257	$144.13	$144.15	$144.10
Purchase #3	$63.81	6.234%	$67.7879	$67.79	$67.80	$67.80
Purchase #4	$37.62	13.197%	$42.5847	$42.58	$42.60	$42.60
Purchase #5	$30.69	9.117%	$33.488	$33.49	$33.50	$33.50
Purchase #6	$47.74	5.142%	$50.1948	$50.19	$50.20	$50.20
Purchase #7	$42.93	8.744%	$46.6838	$46.68	$46.70	$46.70
7 purchase totals =	$399.60		$438.9451	$438.94	$439.05	$439.00