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	$56.50	8.529%	$61.3189	$61.32	$61.30	$61.30
Purchase #2	$127.56	6.640%	$136.03	$136.03	$136.05	$136.00
Purchase #3	$46.47	6.554%	$49.5156	$49.52	$49.50	$49.50
Purchase #4	$162.61	6.551%	$173.2626	$173.26	$173.25	$173.30
Purchase #5	$107.29	10.622%	$118.6863	$118.69	$118.70	$118.70
Purchase #6	$59.37	11.125%	$65.9749	$65.97	$65.95	$66.00
Purchase #7	$174.89	9.714%	$191.8788	$191.88	$191.90	$191.90
7 purchase totals =	$734.69		$796.6671	$796.67	$796.65	$796.70