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	$144.70	5.466%	$152.6093	$152.61	$152.60	$152.60
Purchase #2	$180.72	10.140%	$199.045	$199.05	$199.05	$199.00
Purchase #3	$49.68	4.810%	$52.0696	$52.07	$52.05	$52.10
Purchase #4	$170.94	8.554%	$185.5622	$185.56	$185.55	$185.60
Purchase #5	$40.45	6.548%	$43.0987	$43.10	$43.10	$43.10
Purchase #6	$122.93	4.251%	$128.1558	$128.16	$128.15	$128.20
Purchase #7	$93.26	7.806%	$100.5399	$100.54	$100.55	$100.50
7 purchase totals =	$802.68		$861.0805	$861.09	$861.05	$861.10