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	$146.43	4.606%	$153.1746	$153.17	$153.15	$153.20
Purchase #2	$159.49	12.239%	$179.01	$179.01	$179.00	$179.00
Purchase #3	$167.30	3.728%	$173.5369	$173.54	$173.55	$173.50
Purchase #4	$93.96	10.338%	$103.6736	$103.67	$103.65	$103.70
Purchase #5	$241.73	9.236%	$264.0562	$264.06	$264.05	$264.10
Purchase #6	$208.59	10.500%	$230.492	$230.49	$230.50	$230.50
Purchase #7	$49.57	9.555%	$54.3064	$54.31	$54.30	$54.30
7 purchase totals =	$1,067.07		$1,158.2497	$1,158.25	$1,158.20	$1,158.30