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	$202.41	13.786%	$230.3142	$230.31	$230.30	$230.30
Purchase #2	$142.56	11.447%	$158.8788	$158.88	$158.90	$158.90
Purchase #3	$77.72	13.444%	$88.1687	$88.17	$88.15	$88.20
Purchase #4	$234.90	7.316%	$252.0853	$252.09	$252.10	$252.10
Purchase #5	$179.29	9.379%	$196.1056	$196.11	$196.10	$196.10
Purchase #6	$176.44	9.687%	$193.5317	$193.53	$193.55	$193.50
Purchase #7	$98.64	13.405%	$111.8627	$111.86	$111.85	$111.90
7 purchase totals =	$1,111.96		$1,230.9470	$1,230.95	$1,230.95	$1,231.00