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	$56.59	7.810%	$61.0097	$61.01	$61.00	$61.00
Purchase #2	$20.52	5.103%	$21.5671	$21.57	$21.55	$21.60
Purchase #3	$46.57	11.836%	$52.082	$52.08	$52.10	$52.10
Purchase #4	$52.69	6.789%	$56.2671	$56.27	$56.25	$56.30
Purchase #5	$55.55	10.650%	$61.4661	$61.47	$61.45	$61.50
Purchase #6	$194.26	3.705%	$201.4573	$201.46	$201.45	$201.50
Purchase #7	$129.69	7.229%	$139.0653	$139.07	$139.05	$139.10
7 purchase totals =	$555.87		$592.9146	$592.93	$592.85	$593.10