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	$198.50	12.622%	$223.5547	$223.55	$223.55	$223.60
Purchase #2	$62.71	7.290%	$67.2816	$67.28	$67.30	$67.30
Purchase #3	$193.30	3.832%	$200.7073	$200.71	$200.70	$200.70
Purchase #4	$230.59	11.489%	$257.0825	$257.08	$257.10	$257.10
Purchase #5	$160.78	7.472%	$172.7935	$172.79	$172.80	$172.80
Purchase #6	$88.75	4.646%	$92.8733	$92.87	$92.85	$92.90
Purchase #7	$139.87	3.304%	$144.4913	$144.49	$144.50	$144.50
7 purchase totals =	$1,074.50		$1,158.7842	$1,158.77	$1,158.80	$1,158.90