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	$112.32	5.296%	$118.2685	$118.27	$118.25	$118.30
Purchase #2	$249.76	10.406%	$275.75	$275.75	$275.75	$275.80
Purchase #3	$43.56	13.735%	$49.543	$49.54	$49.55	$49.50
Purchase #4	$105.50	13.799%	$120.0579	$120.06	$120.05	$120.10
Purchase #5	$104.88	9.195%	$114.5237	$114.52	$114.50	$114.50
Purchase #6	$121.88	4.775%	$127.6998	$127.70	$127.70	$127.70
Purchase #7	$247.47	10.175%	$272.6501	$272.65	$272.65	$272.70
7 purchase totals =	$985.37		$1,078.4930	$1,078.49	$1,078.45	$1,078.60