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	$53.86	10.160%	$59.3322	$59.33	$59.35	$59.30
Purchase #2	$18.87	6.674%	$20.1294	$20.13	$20.15	$20.10
Purchase #3	$215.33	11.810%	$240.7605	$240.76	$240.75	$240.80
Purchase #4	$107.52	4.746%	$112.6229	$112.62	$112.60	$112.60
Purchase #5	$45.41	7.866%	$48.982	$48.98	$49.00	$49.00
Purchase #6	$210.64	6.715%	$224.7845	$224.78	$224.80	$224.80
Purchase #7	$158.74	10.512%	$175.4267	$175.43	$175.45	$175.40
7 purchase totals =	$810.37		$882.0382	$882.03	$882.10	$882.00