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	$212.50	8.456%	$230.469	$230.47	$230.45	$230.50
Purchase #2	$165.29	8.267%	$178.9545	$178.95	$178.95	$179.00
Purchase #3	$240.61	7.838%	$259.469	$259.47	$259.45	$259.50
Purchase #4	$164.58	5.474%	$173.5891	$173.59	$173.60	$173.60
Purchase #5	$161.74	4.127%	$168.415	$168.42	$168.40	$168.40
Purchase #6	$98.89	12.748%	$111.4965	$111.50	$111.50	$111.50
Purchase #7	$57.98	4.866%	$60.8013	$60.80	$60.80	$60.80
7 purchase totals =	$1,101.59		$1,183.1944	$1,183.20	$1,183.15	$1,183.30