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	$211.56	3.338%	$218.6219	$218.62	$218.60	$218.60
Purchase #2	$77.99	3.308%	$80.5699	$80.57	$80.55	$80.60
Purchase #3	$101.45	9.136%	$110.7185	$110.72	$110.70	$110.70
Purchase #4	$144.26	5.330%	$151.9491	$151.95	$151.95	$151.90
Purchase #5	$101.96	12.670%	$114.8783	$114.88	$114.90	$114.90
Purchase #6	$194.73	10.218%	$214.6275	$214.63	$214.65	$214.60
Purchase #7	$101.67	9.365%	$111.1914	$111.19	$111.20	$111.20
7 purchase totals =	$933.62		$1,002.5566	$1,002.56	$1,002.55	$1,002.50