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	$223.25	13.394%	$253.1521	$253.15	$253.15	$253.20
Purchase #2	$72.58	7.464%	$77.9974	$78.00	$78.00	$78.00
Purchase #3	$10.52	10.297%	$11.6032	$11.60	$11.60	$11.60
Purchase #4	$158.91	11.866%	$177.7663	$177.77	$177.75	$177.80
Purchase #5	$76.83	7.186%	$82.351	$82.35	$82.35	$82.40
Purchase #6	$242.76	5.358%	$255.7671	$255.77	$255.75	$255.80
Purchase #7	$62.54	5.147%	$65.7589	$65.76	$65.75	$65.80
7 purchase totals =	$847.39		$924.3960	$924.40	$924.35	$924.60