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	$63.46	11.267%	$70.61	$70.61	$70.60	$70.60
Purchase #2	$191.52	13.817%	$217.9823	$217.98	$218.00	$218.00
Purchase #3	$46.82	8.633%	$50.862	$50.86	$50.85	$50.90
Purchase #4	$81.45	11.439%	$90.7671	$90.77	$90.75	$90.80
Purchase #5	$130.26	3.343%	$134.6146	$134.61	$134.60	$134.60
Purchase #6	$111.71	5.833%	$118.226	$118.23	$118.25	$118.20
Purchase #7	$63.49	7.631%	$68.3349	$68.33	$68.35	$68.30
7 purchase totals =	$688.71		$751.3969	$751.39	$751.40	$751.40