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	$236.83	4.707%	$247.9776	$247.98	$248.00	$248.00
Purchase #2	$98.89	13.137%	$111.8812	$111.88	$111.90	$111.90
Purchase #3	$152.65	4.340%	$159.275	$159.28	$159.30	$159.30
Purchase #4	$118.45	7.612%	$127.4664	$127.47	$127.45	$127.50
Purchase #5	$145.86	5.575%	$153.9917	$153.99	$154.00	$154.00
Purchase #6	$164.88	6.706%	$175.9369	$175.94	$175.95	$175.90
Purchase #7	$226.94	11.460%	$252.9473	$252.95	$252.95	$252.90
7 purchase totals =	$1,144.50		$1,229.4761	$1,229.49	$1,229.55	$1,229.50