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	$124.61	10.612%	$137.8336	$137.83	$137.85	$137.80
Purchase #2	$226.79	11.614%	$253.1294	$253.13	$253.15	$253.10
Purchase #3	$40.67	5.324%	$42.8353	$42.84	$42.85	$42.80
Purchase #4	$100.78	4.217%	$105.0299	$105.03	$105.05	$105.00
Purchase #5	$208.26	9.230%	$227.4824	$227.48	$227.50	$227.50
Purchase #6	$212.51	8.679%	$230.9537	$230.95	$230.95	$231.00
Purchase #7	$99.48	5.103%	$104.5565	$104.56	$104.55	$104.60
7 purchase totals =	$1,013.10		$1,101.8208	$1,101.82	$1,101.90	$1,101.80