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	$239.98	3.395%	$248.1273	$248.13	$248.15	$248.10
Purchase #2	$52.78	9.352%	$57.716	$57.72	$57.70	$57.70
Purchase #3	$179.26	6.474%	$190.8653	$190.87	$190.85	$190.90
Purchase #4	$204.65	12.750%	$230.7429	$230.74	$230.75	$230.70
Purchase #5	$177.85	10.521%	$196.5616	$196.56	$196.55	$196.60
Purchase #6	$131.95	9.598%	$144.6146	$144.61	$144.60	$144.60
Purchase #7	$136.39	5.773%	$144.2638	$144.26	$144.25	$144.30
7 purchase totals =	$1,122.86		$1,212.8915	$1,212.89	$1,212.85	$1,212.90