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	$234.72	11.151%	$260.8936	$260.89	$260.90	$260.90
Purchase #2	$129.74	12.333%	$145.7408	$145.74	$145.75	$145.70
Purchase #3	$132.75	6.305%	$141.1199	$141.12	$141.10	$141.10
Purchase #4	$111.68	11.595%	$124.6293	$124.63	$124.65	$124.60
Purchase #5	$110.34	11.716%	$123.2674	$123.27	$123.25	$123.30
Purchase #6	$134.36	7.627%	$144.6076	$144.61	$144.60	$144.60
Purchase #7	$139.99	3.585%	$145.0086	$145.01	$145.00	$145.00
7 purchase totals =	$993.58		$1,085.2672	$1,085.27	$1,085.25	$1,085.20