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	$182.61	7.488%	$196.2838	$196.28	$196.30	$196.30
Purchase #2	$156.36	10.826%	$173.2875	$173.29	$173.30	$173.30
Purchase #3	$204.84	10.577%	$226.5059	$226.51	$226.50	$226.50
Purchase #4	$50.50	4.176%	$52.6089	$52.61	$52.60	$52.60
Purchase #5	$25.85	10.250%	$28.4996	$28.50	$28.50	$28.50
Purchase #6	$210.81	3.106%	$217.3578	$217.36	$217.35	$217.40
Purchase #7	$232.60	11.593%	$259.5653	$259.57	$259.55	$259.60
7 purchase totals =	$1,063.57		$1,154.1088	$1,154.12	$1,154.10	$1,154.20