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	$74.37	9.563%	$81.482	$81.48	$81.50	$81.50
Purchase #2	$47.72	10.153%	$52.565	$52.57	$52.55	$52.60
Purchase #3	$91.39	6.275%	$97.1247	$97.12	$97.10	$97.10
Purchase #4	$76.65	8.518%	$83.179	$83.18	$83.20	$83.20
Purchase #5	$90.60	6.463%	$96.4555	$96.46	$96.45	$96.50
Purchase #6	$52.60	4.610%	$55.0249	$55.02	$55.00	$55.00
Purchase #7	$102.38	3.514%	$105.9776	$105.98	$106.00	$106.00
7 purchase totals =	$535.71		$571.8087	$571.81	$571.80	$571.90