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	$111.72	13.746%	$127.077	$127.08	$127.10	$127.10
Purchase #2	$236.42	9.356%	$258.5395	$258.54	$258.55	$258.50
Purchase #3	$221.70	13.703%	$252.0796	$252.08	$252.10	$252.10
Purchase #4	$120.29	4.178%	$125.3157	$125.32	$125.30	$125.30
Purchase #5	$153.35	9.828%	$168.4212	$168.42	$168.40	$168.40
Purchase #6	$31.71	3.143%	$32.7066	$32.71	$32.70	$32.70
Purchase #7	$71.61	9.602%	$78.486	$78.49	$78.50	$78.50
7 purchase totals =	$946.80		$1,042.6256	$1,042.64	$1,042.65	$1,042.60