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	$80.34	10.202%	$88.5363	$88.54	$88.55	$88.50
Purchase #2	$176.40	9.553%	$193.2515	$193.25	$193.25	$193.30
Purchase #3	$48.67	5.388%	$51.2923	$51.29	$51.30	$51.30
Purchase #4	$238.65	12.753%	$269.085	$269.09	$269.10	$269.10
Purchase #5	$90.58	3.866%	$94.0818	$94.08	$94.10	$94.10
Purchase #6	$136.61	13.333%	$154.8242	$154.82	$154.80	$154.80
Purchase #7	$127.47	12.589%	$143.5172	$143.52	$143.50	$143.50
7 purchase totals =	$898.72		$994.5883	$994.59	$994.60	$994.60