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	$125.51	11.218%	$139.5897	$139.59	$139.60	$139.60
Purchase #2	$115.63	10.354%	$127.6023	$127.60	$127.60	$127.60
Purchase #3	$62.37	11.733%	$69.6879	$69.69	$69.70	$69.70
Purchase #4	$11.43	12.765%	$12.889	$12.89	$12.90	$12.90
Purchase #5	$146.32	11.769%	$163.5404	$163.54	$163.55	$163.50
Purchase #6	$67.60	6.482%	$71.9818	$71.98	$72.00	$72.00
Purchase #7	$90.61	8.273%	$98.1062	$98.11	$98.10	$98.10
7 purchase totals =	$619.47		$683.3973	$683.40	$683.45	$683.40