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	$145.79	7.382%	$156.5522	$156.55	$156.55	$156.60
Purchase #2	$59.81	12.264%	$67.1451	$67.15	$67.15	$67.10
Purchase #3	$131.31	9.402%	$143.6558	$143.66	$143.65	$143.70
Purchase #4	$46.97	3.271%	$48.5064	$48.51	$48.50	$48.50
Purchase #5	$172.46	13.107%	$195.0643	$195.06	$195.05	$195.10
Purchase #6	$97.93	10.413%	$108.1275	$108.13	$108.15	$108.10
Purchase #7	$238.30	4.274%	$248.4849	$248.48	$248.50	$248.50
7 purchase totals =	$892.57		$967.5362	$967.54	$967.55	$967.60