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	$244.99	9.736%	$268.8422	$268.84	$268.85	$268.80
Purchase #2	$117.69	8.466%	$127.6536	$127.65	$127.65	$127.70
Purchase #3	$21.27	3.458%	$22.0055	$22.01	$22.00	$22.00
Purchase #4	$48.94	3.201%	$50.5066	$50.51	$50.50	$50.50
Purchase #5	$10.68	11.400%	$11.8975	$11.90	$11.90	$11.90
Purchase #6	$154.25	11.433%	$171.8854	$171.89	$171.90	$171.90
Purchase #7	$220.78	10.820%	$244.6684	$244.67	$244.65	$244.70
7 purchase totals =	$818.60		$897.4592	$897.47	$897.45	$897.50