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	$137.68	12.872%	$155.4022	$155.40	$155.40	$155.40
Purchase #2	$59.73	3.576%	$61.8659	$61.87	$61.85	$61.90
Purchase #3	$139.98	3.244%	$144.521	$144.52	$144.50	$144.50
Purchase #4	$175.60	8.630%	$190.7543	$190.75	$190.75	$190.80
Purchase #5	$130.59	6.632%	$139.2507	$139.25	$139.25	$139.30
Purchase #6	$184.64	10.753%	$204.4943	$204.49	$204.50	$204.50
Purchase #7	$200.71	11.686%	$224.165	$224.17	$224.15	$224.20
7 purchase totals =	$1,028.93		$1,120.4534	$1,120.45	$1,120.40	$1,120.60