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	$217.52	4.489%	$227.2845	$227.28	$227.30	$227.30
Purchase #2	$227.77	12.650%	$256.5829	$256.58	$256.60	$256.60
Purchase #3	$48.33	10.407%	$53.3597	$53.36	$53.35	$53.40
Purchase #4	$144.28	12.716%	$162.6266	$162.63	$162.65	$162.60
Purchase #5	$104.55	6.197%	$111.029	$111.03	$111.05	$111.00
Purchase #6	$211.54	7.139%	$226.6418	$226.64	$226.65	$226.60
Purchase #7	$159.62	5.348%	$168.1565	$168.16	$168.15	$168.20
7 purchase totals =	$1,113.61		$1,205.6810	$1,205.68	$1,205.75	$1,205.70