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	$88.28	4.105%	$91.9039	$91.90	$91.90	$91.90
Purchase #2	$103.65	9.581%	$113.5807	$113.58	$113.60	$113.60
Purchase #3	$38.85	8.436%	$42.1274	$42.13	$42.15	$42.10
Purchase #4	$145.86	8.533%	$158.3062	$158.31	$158.30	$158.30
Purchase #5	$181.45	5.403%	$191.2537	$191.25	$191.25	$191.30
Purchase #6	$208.58	10.686%	$230.8689	$230.87	$230.85	$230.90
Purchase #7	$136.72	3.693%	$141.7691	$141.77	$141.75	$141.80
7 purchase totals =	$903.39		$969.8099	$969.81	$969.80	$969.90