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	$101.26	3.195%	$104.4953	$104.50	$104.50	$104.50
Purchase #2	$160.93	4.837%	$168.7142	$168.71	$168.70	$168.70
Purchase #3	$206.77	7.585%	$222.4535	$222.45	$222.45	$222.50
Purchase #4	$230.64	10.161%	$254.0753	$254.08	$254.10	$254.10
Purchase #5	$234.33	6.578%	$249.7442	$249.74	$249.75	$249.70
Purchase #6	$64.38	11.136%	$71.5494	$71.55	$71.55	$71.50
Purchase #7	$143.61	10.406%	$158.5541	$158.55	$158.55	$158.60
7 purchase totals =	$1,141.92		$1,229.5860	$1,229.58	$1,229.60	$1,229.60