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	$199.71	8.784%	$217.2525	$217.25	$217.25	$217.30
Purchase #2	$169.40	5.430%	$178.5984	$178.60	$178.60	$178.60
Purchase #3	$171.83	5.484%	$181.2532	$181.25	$181.25	$181.30
Purchase #4	$50.27	4.655%	$52.6101	$52.61	$52.60	$52.60
Purchase #5	$248.78	8.453%	$269.8094	$269.81	$269.80	$269.80
Purchase #6	$75.66	13.508%	$85.8802	$85.88	$85.90	$85.90
Purchase #7	$110.59	8.200%	$119.6584	$119.66	$119.65	$119.70
7 purchase totals =	$1,026.24		$1,105.0622	$1,105.06	$1,105.05	$1,105.20