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	$168.54	13.310%	$190.9727	$190.97	$190.95	$191.00
Purchase #2	$131.93	4.140%	$137.3919	$137.39	$137.40	$137.40
Purchase #3	$107.27	10.570%	$118.6084	$118.61	$118.60	$118.60
Purchase #4	$131.25	5.545%	$138.5278	$138.53	$138.55	$138.50
Purchase #5	$238.40	7.724%	$256.814	$256.81	$256.80	$256.80
Purchase #6	$39.28	10.255%	$43.3082	$43.31	$43.30	$43.30
Purchase #7	$53.56	10.251%	$59.0504	$59.05	$59.05	$59.10
7 purchase totals =	$870.23		$944.6734	$944.67	$944.65	$944.70