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	$230.58	11.433%	$256.9422	$256.94	$256.95	$256.90
Purchase #2	$58.25	6.597%	$62.0928	$62.09	$62.10	$62.10
Purchase #3	$90.45	12.444%	$101.7056	$101.71	$101.70	$101.70
Purchase #4	$92.78	4.141%	$96.622	$96.62	$96.60	$96.60
Purchase #5	$38.71	8.834%	$42.1296	$42.13	$42.15	$42.10
Purchase #6	$186.83	9.611%	$204.7862	$204.79	$204.80	$204.80
Purchase #7	$128.61	11.373%	$143.2368	$143.24	$143.25	$143.20
7 purchase totals =	$826.21		$907.5152	$907.52	$907.55	$907.40