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	$178.45	6.774%	$190.5382	$190.54	$190.55	$190.50
Purchase #2	$147.72	4.226%	$153.9626	$153.96	$153.95	$154.00
Purchase #3	$179.31	8.434%	$194.433	$194.43	$194.45	$194.40
Purchase #4	$65.98	10.149%	$72.6763	$72.68	$72.70	$72.70
Purchase #5	$121.59	13.314%	$137.7785	$137.78	$137.80	$137.80
Purchase #6	$161.77	6.429%	$172.1702	$172.17	$172.15	$172.20
Purchase #7	$109.26	5.626%	$115.407	$115.41	$115.40	$115.40
7 purchase totals =	$964.08		$1,036.9658	$1,036.97	$1,037.00	$1,037.00