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	$214.78	5.721%	$227.0676	$227.07	$227.05	$227.10
Purchase #2	$227.46	3.180%	$234.6932	$234.69	$234.70	$234.70
Purchase #3	$46.81	7.402%	$50.2749	$50.27	$50.25	$50.30
Purchase #4	$222.84	11.503%	$248.4733	$248.47	$248.45	$248.50
Purchase #5	$67.95	7.129%	$72.7942	$72.79	$72.80	$72.80
Purchase #6	$38.89	6.451%	$41.3988	$41.40	$41.40	$41.40
Purchase #7	$89.69	12.556%	$100.9515	$100.95	$100.95	$101.00
7 purchase totals =	$908.42		$975.6535	$975.64	$975.60	$975.80