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	$50.52	10.233%	$55.6897	$55.69	$55.70	$55.70
Purchase #2	$158.48	11.772%	$177.1363	$177.14	$177.15	$177.10
Purchase #3	$100.74	10.682%	$111.501	$111.50	$111.50	$111.50
Purchase #4	$71.39	7.175%	$76.5122	$76.51	$76.50	$76.50
Purchase #5	$59.40	9.190%	$64.8589	$64.86	$64.85	$64.90
Purchase #6	$206.39	8.755%	$224.4594	$224.46	$224.45	$224.50
Purchase #7	$45.32	8.695%	$49.2606	$49.26	$49.25	$49.30
7 purchase totals =	$692.24		$759.4181	$759.42	$759.40	$759.50