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	$69.47	3.728%	$72.0598	$72.06	$72.05	$72.10
Purchase #2	$228.31	10.194%	$251.5839	$251.58	$251.60	$251.60
Purchase #3	$118.67	6.489%	$126.3705	$126.37	$126.35	$126.40
Purchase #4	$96.63	7.221%	$103.6077	$103.61	$103.60	$103.60
Purchase #5	$15.64	9.504%	$17.1264	$17.13	$17.15	$17.10
Purchase #6	$102.49	8.857%	$111.5675	$111.57	$111.55	$111.60
Purchase #7	$247.38	11.336%	$275.423	$275.42	$275.40	$275.40
7 purchase totals =	$878.59		$957.7388	$957.74	$957.70	$957.80