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	$92.45	3.248%	$95.4528	$95.45	$95.45	$95.50
Purchase #2	$215.40	11.425%	$240.0095	$240.01	$240.00	$240.00
Purchase #3	$62.81	5.235%	$66.0981	$66.10	$66.10	$66.10
Purchase #4	$78.64	10.428%	$86.8406	$86.84	$86.85	$86.80
Purchase #5	$40.65	12.185%	$45.6032	$45.60	$45.60	$45.60
Purchase #6	$200.92	13.675%	$228.3958	$228.40	$228.40	$228.40
Purchase #7	$94.36	9.588%	$103.4072	$103.41	$103.40	$103.40
7 purchase totals =	$785.23		$865.8072	$865.81	$865.80	$865.80