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	$60.93	11.245%	$67.7816	$67.78	$67.80	$67.80
Purchase #2	$111.30	11.720%	$124.3444	$124.34	$124.35	$124.30
Purchase #3	$54.42	13.195%	$61.6007	$61.60	$61.60	$61.60
Purchase #4	$17.55	5.125%	$18.4494	$18.45	$18.45	$18.40
Purchase #5	$188.75	12.478%	$212.3022	$212.30	$212.30	$212.30
Purchase #6	$168.66	9.719%	$185.0521	$185.05	$185.05	$185.10
Purchase #7	$215.72	8.371%	$233.7779	$233.78	$233.80	$233.80
7 purchase totals =	$817.33		$903.3083	$903.30	$903.35	$903.30