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	$207.92	7.773%	$224.0816	$224.08	$224.10	$224.10
Purchase #2	$186.70	13.379%	$211.6786	$211.68	$211.70	$211.70
Purchase #3	$79.54	8.785%	$86.5276	$86.53	$86.55	$86.50
Purchase #4	$215.26	8.553%	$233.6712	$233.67	$233.65	$233.70
Purchase #5	$133.69	4.658%	$139.9173	$139.92	$139.90	$139.90
Purchase #6	$10.52	3.508%	$10.889	$10.89	$10.90	$10.90
Purchase #7	$74.76	4.418%	$78.0629	$78.06	$78.05	$78.10
7 purchase totals =	$908.39		$984.8282	$984.83	$984.85	$984.90