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	$175.89	3.105%	$181.3514	$181.35	$181.35	$181.40
Purchase #2	$112.65	4.200%	$117.3813	$117.38	$117.40	$117.40
Purchase #3	$105.96	13.783%	$120.5645	$120.56	$120.55	$120.60
Purchase #4	$119.56	6.613%	$127.4665	$127.47	$127.45	$127.50
Purchase #5	$217.98	9.223%	$238.0843	$238.08	$238.10	$238.10
Purchase #6	$196.55	9.325%	$214.8783	$214.88	$214.90	$214.90
Purchase #7	$180.48	7.575%	$194.1514	$194.15	$194.15	$194.20
7 purchase totals =	$1,109.07		$1,193.8777	$1,193.87	$1,193.90	$1,194.10