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	$217.59	3.590%	$225.4015	$225.40	$225.40	$225.40
Purchase #2	$48.46	4.745%	$50.7594	$50.76	$50.75	$50.80
Purchase #3	$96.87	6.129%	$102.8072	$102.81	$102.80	$102.80
Purchase #4	$130.62	8.440%	$141.6443	$141.64	$141.65	$141.60
Purchase #5	$101.92	9.415%	$111.5158	$111.52	$111.50	$111.50
Purchase #6	$60.83	13.672%	$69.1467	$69.15	$69.15	$69.10
Purchase #7	$27.96	13.267%	$31.6695	$31.67	$31.65	$31.70
7 purchase totals =	$684.25		$732.9444	$732.95	$732.90	$732.90