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	$188.99	10.367%	$208.5826	$208.58	$208.60	$208.60
Purchase #2	$43.25	12.278%	$48.5602	$48.56	$48.55	$48.60
Purchase #3	$8.46	5.422%	$8.9187	$8.92	$8.90	$8.90
Purchase #4	$48.81	10.270%	$53.8228	$53.82	$53.80	$53.80
Purchase #5	$119.66	9.848%	$131.4441	$131.44	$131.45	$131.40
Purchase #6	$116.26	9.664%	$127.4954	$127.50	$127.50	$127.50
Purchase #7	$59.60	4.586%	$62.3333	$62.33	$62.35	$62.30
7 purchase totals =	$585.03		$641.1571	$641.15	$641.15	$641.10