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	$49.92	13.439%	$56.6287	$56.63	$56.65	$56.60
Purchase #2	$20.46	9.751%	$22.4551	$22.46	$22.45	$22.50
Purchase #3	$60.38	6.621%	$64.3778	$64.38	$64.40	$64.40
Purchase #4	$97.45	12.236%	$109.374	$109.37	$109.35	$109.40
Purchase #5	$118.98	6.844%	$127.123	$127.12	$127.10	$127.10
Purchase #6	$142.70	8.789%	$155.2419	$155.24	$155.25	$155.20
Purchase #7	$244.52	6.724%	$260.9615	$260.96	$260.95	$261.00
7 purchase totals =	$734.41		$796.1620	$796.16	$796.15	$796.20