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	$9.87	3.720%	$10.2372	$10.24	$10.25	$10.20
Purchase #2	$212.70	8.796%	$231.4091	$231.41	$231.40	$231.40
Purchase #3	$51.78	4.283%	$53.9977	$54.00	$54.00	$54.00
Purchase #4	$74.77	10.333%	$82.496	$82.50	$82.50	$82.50
Purchase #5	$231.51	10.275%	$255.2977	$255.30	$255.30	$255.30
Purchase #6	$127.31	8.820%	$138.5387	$138.54	$138.55	$138.50
Purchase #7	$154.25	4.126%	$160.6144	$160.61	$160.60	$160.60
7 purchase totals =	$862.19		$932.5908	$932.60	$932.60	$932.50