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	$109.77	12.844%	$123.8689	$123.87	$123.85	$123.90
Purchase #2	$49.95	8.385%	$54.1383	$54.14	$54.15	$54.10
Purchase #3	$187.29	3.613%	$194.0568	$194.06	$194.05	$194.10
Purchase #4	$156.98	9.349%	$171.6561	$171.66	$171.65	$171.70
Purchase #5	$205.94	12.511%	$231.7052	$231.71	$231.70	$231.70
Purchase #6	$63.46	6.578%	$67.6344	$67.63	$67.65	$67.60
Purchase #7	$124.62	12.236%	$139.8685	$139.87	$139.85	$139.90
7 purchase totals =	$898.01		$982.9282	$982.94	$982.90	$983.00