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	$198.30	10.866%	$219.8473	$219.85	$219.85	$219.80
Purchase #2	$54.76	5.412%	$57.7236	$57.72	$57.70	$57.70
Purchase #3	$120.27	8.465%	$130.4509	$130.45	$130.45	$130.50
Purchase #4	$55.35	9.235%	$60.4616	$60.46	$60.45	$60.50
Purchase #5	$48.77	12.794%	$55.0096	$55.01	$55.00	$55.00
Purchase #6	$144.79	9.569%	$158.645	$158.65	$158.65	$158.60
Purchase #7	$37.66	11.646%	$42.0459	$42.05	$42.05	$42.00
7 purchase totals =	$659.90		$724.1839	$724.19	$724.15	$724.10