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	$12.77	13.717%	$14.5217	$14.52	$14.50	$14.50
Purchase #2	$172.56	11.535%	$192.4648	$192.46	$192.45	$192.50
Purchase #3	$80.25	13.519%	$91.099	$91.10	$91.10	$91.10
Purchase #4	$93.51	6.618%	$99.6985	$99.70	$99.70	$99.70
Purchase #5	$69.70	12.104%	$78.1365	$78.14	$78.15	$78.10
Purchase #6	$31.41	8.212%	$33.9894	$33.99	$34.00	$34.00
Purchase #7	$164.97	4.574%	$172.5157	$172.52	$172.50	$172.50
7 purchase totals =	$625.17		$682.4256	$682.43	$682.40	$682.40