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	$214.37	11.140%	$238.2508	$238.25	$238.25	$238.30
Purchase #2	$153.56	7.783%	$165.5116	$165.51	$165.50	$165.50
Purchase #3	$48.50	12.470%	$54.548	$54.55	$54.55	$54.50
Purchase #4	$171.58	13.325%	$194.443	$194.44	$194.45	$194.40
Purchase #5	$118.36	7.808%	$127.6015	$127.60	$127.60	$127.60
Purchase #6	$39.44	3.663%	$40.8847	$40.88	$40.90	$40.90
Purchase #7	$91.89	5.186%	$96.6554	$96.66	$96.65	$96.70
7 purchase totals =	$837.70		$917.8950	$917.89	$917.90	$917.90