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	$132.98	4.768%	$139.3205	$139.32	$139.30	$139.30
Purchase #2	$94.93	10.170%	$104.5844	$104.58	$104.60	$104.60
Purchase #3	$58.42	10.479%	$64.5418	$64.54	$64.55	$64.50
Purchase #4	$153.98	11.727%	$172.0372	$172.04	$172.05	$172.00
Purchase #5	$101.56	4.330%	$105.9575	$105.96	$105.95	$106.00
Purchase #6	$45.64	6.467%	$48.5915	$48.59	$48.60	$48.60
Purchase #7	$66.57	6.271%	$70.7446	$70.74	$70.75	$70.70
7 purchase totals =	$654.08		$705.7775	$705.77	$705.80	$705.70