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	$51.58	3.355%	$53.3105	$53.31	$53.30	$53.30
Purchase #2	$54.34	6.439%	$57.839	$57.84	$57.85	$57.80
Purchase #3	$122.34	4.236%	$127.5223	$127.52	$127.50	$127.50
Purchase #4	$122.71	6.820%	$131.0788	$131.08	$131.10	$131.10
Purchase #5	$211.39	10.584%	$233.7635	$233.76	$233.75	$233.80
Purchase #6	$115.46	3.458%	$119.4526	$119.45	$119.45	$119.50
Purchase #7	$85.43	7.723%	$92.0278	$92.03	$92.05	$92.00
7 purchase totals =	$763.25		$814.9945	$814.99	$815.00	$815.00