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	$58.72	10.732%	$65.0218	$65.02	$65.00	$65.00
Purchase #2	$182.39	5.516%	$192.4506	$192.45	$192.45	$192.50
Purchase #3	$39.80	4.170%	$41.4597	$41.46	$41.45	$41.50
Purchase #4	$142.99	6.582%	$152.4016	$152.40	$152.40	$152.40
Purchase #5	$171.55	13.113%	$194.0454	$194.05	$194.05	$194.00
Purchase #6	$73.81	10.388%	$81.4774	$81.48	$81.50	$81.50
Purchase #7	$25.97	6.304%	$27.6071	$27.61	$27.60	$27.60
7 purchase totals =	$695.23		$754.4636	$754.47	$754.45	$754.50