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	$11.44	5.543%	$12.0741	$12.07	$12.05	$12.10
Purchase #2	$139.93	4.376%	$146.0533	$146.05	$146.05	$146.10
Purchase #3	$89.27	13.553%	$101.3688	$101.37	$101.35	$101.40
Purchase #4	$164.92	8.499%	$178.9366	$178.94	$178.95	$178.90
Purchase #5	$115.92	10.815%	$128.4567	$128.46	$128.45	$128.50
Purchase #6	$103.74	5.847%	$109.8057	$109.81	$109.80	$109.80
Purchase #7	$105.75	3.630%	$109.5887	$109.59	$109.60	$109.60
7 purchase totals =	$730.97		$786.2839	$786.29	$786.25	$786.40