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	$148.89	5.808%	$157.5375	$157.54	$157.55	$157.50
Purchase #2	$129.88	10.486%	$143.4992	$143.50	$143.50	$143.50
Purchase #3	$90.60	13.230%	$102.5864	$102.59	$102.60	$102.60
Purchase #4	$36.64	9.404%	$40.0856	$40.09	$40.10	$40.10
Purchase #5	$118.70	4.112%	$123.5809	$123.58	$123.60	$123.60
Purchase #6	$230.63	5.826%	$244.0665	$244.07	$244.05	$244.10
Purchase #7	$245.69	11.384%	$273.6593	$273.66	$273.65	$273.70
7 purchase totals =	$1,001.03		$1,085.0154	$1,085.03	$1,085.05	$1,085.10