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	$230.87	3.833%	$239.7192	$239.72	$239.70	$239.70
Purchase #2	$159.64	12.191%	$179.1017	$179.10	$179.10	$179.10
Purchase #3	$94.38	11.577%	$105.3064	$105.31	$105.30	$105.30
Purchase #4	$99.42	11.227%	$110.5819	$110.58	$110.60	$110.60
Purchase #5	$139.40	8.763%	$151.6156	$151.62	$151.60	$151.60
Purchase #6	$158.83	6.155%	$168.606	$168.61	$168.60	$168.60
Purchase #7	$96.42	7.344%	$103.5011	$103.50	$103.50	$103.50
7 purchase totals =	$978.96		$1,058.4319	$1,058.44	$1,058.40	$1,058.40