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	$66.68	4.340%	$69.5739	$69.57	$69.55	$69.60
Purchase #2	$48.56	8.123%	$52.5045	$52.50	$52.50	$52.50
Purchase #3	$97.55	7.689%	$105.0506	$105.05	$105.05	$105.10
Purchase #4	$117.66	13.798%	$133.8947	$133.89	$133.90	$133.90
Purchase #5	$70.32	9.643%	$77.101	$77.10	$77.10	$77.10
Purchase #6	$96.44	9.436%	$105.5401	$105.54	$105.55	$105.50
Purchase #7	$235.66	13.376%	$267.1819	$267.18	$267.20	$267.20
7 purchase totals =	$732.87		$810.8467	$810.83	$810.85	$810.90