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	$115.68	6.755%	$123.4942	$123.49	$123.50	$123.50
Purchase #2	$191.67	13.504%	$217.5531	$217.55	$217.55	$217.60
Purchase #3	$151.77	13.221%	$171.8355	$171.84	$171.85	$171.80
Purchase #4	$101.63	10.829%	$112.6355	$112.64	$112.65	$112.60
Purchase #5	$113.33	8.783%	$123.2838	$123.28	$123.30	$123.30
Purchase #6	$138.66	9.186%	$151.3973	$151.40	$151.40	$151.40
Purchase #7	$193.53	7.669%	$208.3718	$208.37	$208.35	$208.40
7 purchase totals =	$1,006.27		$1,108.5712	$1,108.57	$1,108.60	$1,108.60