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	$131.82	8.230%	$142.6688	$142.67	$142.65	$142.70
Purchase #2	$116.78	9.327%	$127.6721	$127.67	$127.65	$127.70
Purchase #3	$55.81	13.867%	$63.5492	$63.55	$63.55	$63.50
Purchase #4	$180.55	7.211%	$193.5695	$193.57	$193.55	$193.60
Purchase #5	$123.74	3.214%	$127.717	$127.72	$127.70	$127.70
Purchase #6	$68.61	4.512%	$71.7057	$71.71	$71.70	$71.70
Purchase #7	$10.51	5.156%	$11.0519	$11.05	$11.05	$11.10
7 purchase totals =	$687.82		$737.9342	$737.94	$737.85	$738.00