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	$90.44	9.332%	$98.8799	$98.88	$98.90	$98.90
Purchase #2	$205.25	12.268%	$230.4301	$230.43	$230.45	$230.40
Purchase #3	$27.55	13.600%	$31.2968	$31.30	$31.30	$31.30
Purchase #4	$99.25	6.419%	$105.6209	$105.62	$105.60	$105.60
Purchase #5	$115.35	10.332%	$127.268	$127.27	$127.25	$127.30
Purchase #6	$229.75	11.147%	$255.3602	$255.36	$255.35	$255.40
Purchase #7	$187.77	4.124%	$195.5136	$195.51	$195.50	$195.50
7 purchase totals =	$955.36		$1,044.3695	$1,044.37	$1,044.35	$1,044.40