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	$75.69	10.796%	$83.8615	$83.86	$83.85	$83.90
Purchase #2	$94.42	13.784%	$107.4349	$107.43	$107.45	$107.40
Purchase #3	$22.78	6.858%	$24.3423	$24.34	$24.35	$24.30
Purchase #4	$193.37	13.157%	$218.8117	$218.81	$218.80	$218.80
Purchase #5	$17.35	13.226%	$19.6447	$19.64	$19.65	$19.60
Purchase #6	$167.54	10.501%	$185.1334	$185.13	$185.15	$185.10
Purchase #7	$100.31	3.503%	$103.8239	$103.82	$103.80	$103.80
7 purchase totals =	$671.46		$743.0524	$743.03	$743.05	$742.90