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	$60.36	9.268%	$65.9542	$65.95	$65.95	$66.00
Purchase #2	$243.59	12.134%	$273.1472	$273.15	$273.15	$273.10
Purchase #3	$223.82	3.124%	$230.8121	$230.81	$230.80	$230.80
Purchase #4	$86.70	10.464%	$95.7723	$95.77	$95.75	$95.80
Purchase #5	$52.66	9.121%	$57.4631	$57.46	$57.45	$57.50
Purchase #6	$146.39	3.303%	$151.2253	$151.23	$151.25	$151.20
Purchase #7	$85.58	5.493%	$90.2809	$90.28	$90.30	$90.30
7 purchase totals =	$899.10		$964.6551	$964.65	$964.65	$964.70