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	$59.93	13.159%	$67.8162	$67.82	$67.80	$67.80
Purchase #2	$100.89	6.701%	$107.6506	$107.65	$107.65	$107.70
Purchase #3	$117.83	7.707%	$126.9112	$126.91	$126.90	$126.90
Purchase #4	$156.78	6.621%	$167.1604	$167.16	$167.15	$167.20
Purchase #5	$37.59	11.345%	$41.8546	$41.85	$41.85	$41.90
Purchase #6	$18.52	10.696%	$20.5009	$20.50	$20.50	$20.50
Purchase #7	$228.35	3.755%	$236.9245	$236.92	$236.90	$236.90
7 purchase totals =	$719.89		$768.8184	$768.81	$768.75	$768.90