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	$74.40	5.451%	$78.4555	$78.46	$78.45	$78.50
Purchase #2	$165.78	13.701%	$188.4935	$188.49	$188.50	$188.50
Purchase #3	$38.72	3.710%	$40.1565	$40.16	$40.15	$40.20
Purchase #4	$128.74	7.513%	$138.4122	$138.41	$138.40	$138.40
Purchase #5	$248.66	10.231%	$274.1004	$274.10	$274.10	$274.10
Purchase #6	$189.65	8.484%	$205.7399	$205.74	$205.75	$205.70
Purchase #7	$136.29	5.705%	$144.0653	$144.07	$144.05	$144.10
7 purchase totals =	$982.24		$1,069.4233	$1,069.43	$1,069.40	$1,069.50