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	$209.49	5.520%	$221.0538	$221.05	$221.05	$221.10
Purchase #2	$107.37	5.644%	$113.43	$113.43	$113.45	$113.40
Purchase #3	$55.60	12.505%	$62.5528	$62.55	$62.55	$62.60
Purchase #4	$27.69	8.408%	$30.0182	$30.02	$30.00	$30.00
Purchase #5	$95.53	5.156%	$100.4555	$100.46	$100.45	$100.50
Purchase #6	$5.29	3.306%	$5.4649	$5.46	$5.45	$5.50
Purchase #7	$56.94	4.636%	$59.5797	$59.58	$59.60	$59.60
7 purchase totals =	$557.91		$592.5549	$592.55	$592.55	$592.70