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	$191.86	13.111%	$217.0148	$217.01	$217.00	$217.00
Purchase #2	$19.48	5.726%	$20.5954	$20.60	$20.60	$20.60
Purchase #3	$106.61	9.451%	$116.6857	$116.69	$116.70	$116.70
Purchase #4	$84.97	7.685%	$91.4999	$91.50	$91.50	$91.50
Purchase #5	$49.64	7.622%	$53.4236	$53.42	$53.40	$53.40
Purchase #6	$77.57	10.355%	$85.6024	$85.60	$85.60	$85.60
Purchase #7	$88.57	5.161%	$93.1411	$93.14	$93.15	$93.10
7 purchase totals =	$618.70		$677.9629	$677.96	$677.95	$677.90