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	$146.79	11.843%	$164.1743	$164.17	$164.15	$164.20
Purchase #2	$16.41	11.839%	$18.3528	$18.35	$18.35	$18.40
Purchase #3	$29.60	10.568%	$32.7281	$32.73	$32.75	$32.70
Purchase #4	$103.67	5.579%	$109.4537	$109.45	$109.45	$109.50
Purchase #5	$189.80	13.579%	$215.5729	$215.57	$215.55	$215.60
Purchase #6	$68.52	8.373%	$74.2572	$74.26	$74.25	$74.30
Purchase #7	$66.94	8.326%	$72.5134	$72.51	$72.50	$72.50
7 purchase totals =	$621.73		$687.0524	$687.04	$687.00	$687.20