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	$235.42	6.152%	$249.903	$249.90	$249.90	$249.90
Purchase #2	$229.67	11.121%	$255.2116	$255.21	$255.20	$255.20
Purchase #3	$113.99	12.211%	$127.9093	$127.91	$127.90	$127.90
Purchase #4	$114.90	3.490%	$118.91	$118.91	$118.90	$118.90
Purchase #5	$51.55	8.417%	$55.889	$55.89	$55.90	$55.90
Purchase #6	$115.99	9.575%	$127.096	$127.10	$127.10	$127.10
Purchase #7	$150.85	8.795%	$164.1173	$164.12	$164.10	$164.10
7 purchase totals =	$1,012.37		$1,099.0362	$1,099.04	$1,099.00	$1,099.00