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	$205.40	8.570%	$223.0028	$223.00	$223.00	$223.00
Purchase #2	$246.87	13.176%	$279.3976	$279.40	$279.40	$279.40
Purchase #3	$29.92	5.640%	$31.6075	$31.61	$31.60	$31.60
Purchase #4	$106.94	10.735%	$118.42	$118.42	$118.40	$118.40
Purchase #5	$99.74	8.213%	$107.9316	$107.93	$107.95	$107.90
Purchase #6	$159.82	9.233%	$174.5762	$174.58	$174.60	$174.60
Purchase #7	$142.72	12.526%	$160.5971	$160.60	$160.60	$160.60
7 purchase totals =	$991.41		$1,095.5328	$1,095.54	$1,095.55	$1,095.50