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	$171.73	7.509%	$184.6252	$184.63	$184.65	$184.60
Purchase #2	$80.46	12.795%	$90.7549	$90.75	$90.75	$90.80
Purchase #3	$153.67	4.534%	$160.6374	$160.64	$160.65	$160.60
Purchase #4	$22.94	9.191%	$25.0484	$25.05	$25.05	$25.00
Purchase #5	$175.27	13.581%	$199.0734	$199.07	$199.05	$199.10
Purchase #6	$19.90	12.789%	$22.445	$22.45	$22.45	$22.40
Purchase #7	$127.45	3.514%	$131.9286	$131.93	$131.95	$131.90
7 purchase totals =	$751.42		$814.5129	$814.52	$814.55	$814.40