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	$216.63	6.326%	$230.334	$230.33	$230.35	$230.30
Purchase #2	$45.82	11.480%	$51.0801	$51.08	$51.10	$51.10
Purchase #3	$107.42	6.109%	$113.9823	$113.98	$114.00	$114.00
Purchase #4	$101.82	9.356%	$111.3463	$111.35	$111.35	$111.30
Purchase #5	$226.40	5.363%	$238.5418	$238.54	$238.55	$238.50
Purchase #6	$134.97	3.317%	$139.447	$139.45	$139.45	$139.40
Purchase #7	$74.45	9.162%	$81.2711	$81.27	$81.25	$81.30
7 purchase totals =	$907.51		$966.0026	$966.00	$966.05	$965.90