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	$228.31	13.803%	$259.8236	$259.82	$259.80	$259.80
Purchase #2	$38.77	5.527%	$40.9128	$40.91	$40.90	$40.90
Purchase #3	$219.55	13.649%	$249.5164	$249.52	$249.50	$249.50
Purchase #4	$228.92	5.271%	$240.9864	$240.99	$241.00	$241.00
Purchase #5	$181.60	12.435%	$204.182	$204.18	$204.20	$204.20
Purchase #6	$103.97	10.538%	$114.9264	$114.93	$114.95	$114.90
Purchase #7	$101.78	9.834%	$111.789	$111.79	$111.80	$111.80
7 purchase totals =	$1,102.90		$1,222.1366	$1,222.14	$1,222.15	$1,222.10