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	$146.25	8.748%	$159.044	$159.04	$159.05	$159.00
Purchase #2	$161.45	6.677%	$172.23	$172.23	$172.25	$172.20
Purchase #3	$50.42	7.769%	$54.3371	$54.34	$54.35	$54.30
Purchase #4	$195.46	12.654%	$220.1935	$220.19	$220.20	$220.20
Purchase #5	$144.59	5.224%	$152.1434	$152.14	$152.15	$152.10
Purchase #6	$46.52	10.201%	$51.2655	$51.27	$51.25	$51.30
Purchase #7	$198.78	3.437%	$205.6121	$205.61	$205.60	$205.60
7 purchase totals =	$943.47		$1,014.8256	$1,014.82	$1,014.85	$1,014.70