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	$22.45	13.633%	$25.5106	$25.51	$25.50	$25.50
Purchase #2	$176.66	6.465%	$188.0811	$188.08	$188.10	$188.10
Purchase #3	$199.92	11.852%	$223.6145	$223.61	$223.60	$223.60
Purchase #4	$140.45	4.143%	$146.2688	$146.27	$146.25	$146.30
Purchase #5	$108.81	7.143%	$116.5823	$116.58	$116.60	$116.60
Purchase #6	$131.80	7.356%	$141.4952	$141.50	$141.50	$141.50
Purchase #7	$156.99	10.532%	$173.5242	$173.52	$173.50	$173.50
7 purchase totals =	$937.08		$1,015.0767	$1,015.07	$1,015.05	$1,015.10