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	$115.44	10.388%	$127.4319	$127.43	$127.45	$127.40
Purchase #2	$127.79	5.549%	$134.8811	$134.88	$134.90	$134.90
Purchase #3	$117.51	9.324%	$128.4666	$128.47	$128.45	$128.50
Purchase #4	$12.81	6.595%	$13.6548	$13.65	$13.65	$13.70
Purchase #5	$185.98	3.318%	$192.1508	$192.15	$192.15	$192.20
Purchase #6	$174.37	3.196%	$179.9429	$179.94	$179.95	$179.90
Purchase #7	$179.38	5.144%	$188.6073	$188.61	$188.60	$188.60
7 purchase totals =	$913.28		$965.1354	$965.13	$965.15	$965.20