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	$244.50	9.553%	$267.8571	$267.86	$267.85	$267.90
Purchase #2	$107.82	12.174%	$120.946	$120.95	$120.95	$120.90
Purchase #3	$186.45	4.520%	$194.8775	$194.88	$194.90	$194.90
Purchase #4	$22.32	8.149%	$24.1389	$24.14	$24.15	$24.10
Purchase #5	$182.52	7.615%	$196.4189	$196.42	$196.40	$196.40
Purchase #6	$207.99	3.221%	$214.6894	$214.69	$214.70	$214.70
Purchase #7	$33.75	11.167%	$37.5189	$37.52	$37.50	$37.50
7 purchase totals =	$985.35		$1,056.4467	$1,056.46	$1,056.45	$1,056.40