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	$178.87	9.832%	$196.4565	$196.46	$196.45	$196.50
Purchase #2	$108.25	5.360%	$114.0522	$114.05	$114.05	$114.10
Purchase #3	$193.98	11.281%	$215.8629	$215.86	$215.85	$215.90
Purchase #4	$97.60	11.128%	$108.4609	$108.46	$108.45	$108.50
Purchase #5	$244.46	13.337%	$277.0636	$277.06	$277.05	$277.10
Purchase #6	$42.85	12.336%	$48.136	$48.14	$48.15	$48.10
Purchase #7	$174.55	13.687%	$198.4407	$198.44	$198.45	$198.40
7 purchase totals =	$1,040.56		$1,158.4728	$1,158.47	$1,158.45	$1,158.60