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	$44.43	3.133%	$45.822	$45.82	$45.80	$45.80
Purchase #2	$81.61	9.696%	$89.5229	$89.52	$89.50	$89.50
Purchase #3	$208.93	12.606%	$235.2677	$235.27	$235.25	$235.30
Purchase #4	$114.31	4.683%	$119.6631	$119.66	$119.65	$119.70
Purchase #5	$237.97	8.298%	$257.7168	$257.72	$257.70	$257.70
Purchase #6	$186.63	7.174%	$200.0188	$200.02	$200.00	$200.00
Purchase #7	$138.42	7.522%	$148.832	$148.83	$148.85	$148.80
7 purchase totals =	$1,012.30		$1,096.8433	$1,096.84	$1,096.75	$1,096.80