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	$41.78	5.180%	$43.9442	$43.94	$43.95	$43.90
Purchase #2	$137.96	5.461%	$145.494	$145.49	$145.50	$145.50
Purchase #3	$39.89	4.501%	$41.6854	$41.69	$41.70	$41.70
Purchase #4	$158.27	11.448%	$176.3887	$176.39	$176.40	$176.40
Purchase #5	$158.59	7.436%	$170.3828	$170.38	$170.40	$170.40
Purchase #6	$114.58	11.235%	$127.4531	$127.45	$127.45	$127.50
Purchase #7	$54.73	13.737%	$62.2483	$62.25	$62.25	$62.20
7 purchase totals =	$705.80		$767.5965	$767.59	$767.65	$767.60