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	$145.82	5.663%	$154.0778	$154.08	$154.10	$154.10
Purchase #2	$197.72	8.138%	$213.8105	$213.81	$213.80	$213.80
Purchase #3	$144.47	4.820%	$151.4335	$151.43	$151.45	$151.40
Purchase #4	$172.69	3.836%	$179.3144	$179.31	$179.30	$179.30
Purchase #5	$141.84	13.231%	$160.6069	$160.61	$160.60	$160.60
Purchase #6	$176.67	8.651%	$191.9537	$191.95	$191.95	$192.00
Purchase #7	$158.55	8.683%	$172.3169	$172.32	$172.30	$172.30
7 purchase totals =	$1,137.76		$1,223.5137	$1,223.51	$1,223.50	$1,223.50