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	$57.60	6.169%	$61.1533	$61.15	$61.15	$61.20
Purchase #2	$23.42	5.133%	$24.6221	$24.62	$24.60	$24.60
Purchase #3	$44.63	8.710%	$48.5173	$48.52	$48.50	$48.50
Purchase #4	$102.60	8.220%	$111.0337	$111.03	$111.05	$111.00
Purchase #5	$40.91	4.512%	$42.7559	$42.76	$42.75	$42.80
Purchase #6	$102.48	8.827%	$111.5259	$111.53	$111.55	$111.50
Purchase #7	$205.72	4.852%	$215.7015	$215.70	$215.70	$215.70
7 purchase totals =	$577.36		$615.3097	$615.31	$615.30	$615.30