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	$129.83	9.244%	$141.8315	$141.83	$141.85	$141.80
Purchase #2	$100.99	7.418%	$108.4814	$108.48	$108.50	$108.50
Purchase #3	$135.40	13.472%	$153.6411	$153.64	$153.65	$153.60
Purchase #4	$51.73	3.577%	$53.5804	$53.58	$53.60	$53.60
Purchase #5	$187.37	4.680%	$196.1389	$196.14	$196.15	$196.10
Purchase #6	$29.52	12.134%	$33.102	$33.10	$33.10	$33.10
Purchase #7	$166.94	3.261%	$172.3839	$172.38	$172.40	$172.40
7 purchase totals =	$801.78		$859.1592	$859.15	$859.25	$859.10