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	$247.90	4.841%	$259.9008	$259.90	$259.90	$259.90
Purchase #2	$65.39	10.102%	$71.9957	$72.00	$72.00	$72.00
Purchase #3	$134.77	5.865%	$142.6743	$142.67	$142.65	$142.70
Purchase #4	$77.93	11.711%	$87.0564	$87.06	$87.05	$87.10
Purchase #5	$100.68	10.874%	$111.6279	$111.63	$111.65	$111.60
Purchase #6	$158.55	5.121%	$166.6693	$166.67	$166.65	$166.70
Purchase #7	$208.85	8.621%	$226.855	$226.86	$226.85	$226.90
7 purchase totals =	$994.07		$1,066.7794	$1,066.79	$1,066.75	$1,066.90