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	$109.28	11.864%	$122.245	$122.25	$122.25	$122.20
Purchase #2	$38.94	11.277%	$43.3313	$43.33	$43.35	$43.30
Purchase #3	$55.60	11.627%	$62.0646	$62.06	$62.05	$62.10
Purchase #4	$56.27	12.679%	$63.4045	$63.40	$63.40	$63.40
Purchase #5	$174.47	12.763%	$196.7376	$196.74	$196.75	$196.70
Purchase #6	$174.63	7.124%	$187.0706	$187.07	$187.05	$187.10
Purchase #7	$66.96	8.579%	$72.7045	$72.70	$72.70	$72.70
7 purchase totals =	$676.15		$747.5581	$747.55	$747.55	$747.50