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	$236.92	10.658%	$262.1709	$262.17	$262.15	$262.20
Purchase #2	$87.29	12.613%	$98.2999	$98.30	$98.30	$98.30
Purchase #3	$10.26	4.338%	$10.7051	$10.71	$10.70	$10.70
Purchase #4	$138.47	4.449%	$144.6305	$144.63	$144.65	$144.60
Purchase #5	$14.98	9.448%	$16.3953	$16.40	$16.40	$16.40
Purchase #6	$90.39	10.189%	$99.5998	$99.60	$99.60	$99.60
Purchase #7	$34.93	7.375%	$37.5061	$37.51	$37.50	$37.50
7 purchase totals =	$613.24		$669.3076	$669.32	$669.30	$669.30