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	$182.54	7.770%	$196.7234	$196.72	$196.70	$196.70
Purchase #2	$105.26	12.383%	$118.2943	$118.29	$118.30	$118.30
Purchase #3	$124.68	3.495%	$129.0376	$129.04	$129.05	$129.00
Purchase #4	$84.33	7.232%	$90.4287	$90.43	$90.45	$90.40
Purchase #5	$153.32	3.236%	$158.2814	$158.28	$158.30	$158.30
Purchase #6	$223.87	4.652%	$234.2844	$234.28	$234.30	$234.30
Purchase #7	$172.39	3.578%	$178.5581	$178.56	$178.55	$178.60
7 purchase totals =	$1,046.39		$1,105.6079	$1,105.60	$1,105.65	$1,105.60