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	$217.35	4.413%	$226.9417	$226.94	$226.95	$226.90
Purchase #2	$101.99	8.812%	$110.9774	$110.98	$111.00	$111.00
Purchase #3	$112.53	9.773%	$123.5276	$123.53	$123.55	$123.50
Purchase #4	$78.52	13.489%	$89.1116	$89.11	$89.10	$89.10
Purchase #5	$56.46	10.434%	$62.351	$62.35	$62.35	$62.40
Purchase #6	$230.63	8.323%	$249.8253	$249.83	$249.85	$249.80
Purchase #7	$145.29	3.641%	$150.58	$150.58	$150.60	$150.60
7 purchase totals =	$942.77		$1,013.3146	$1,013.32	$1,013.40	$1,013.30