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	$177.96	10.609%	$196.8398	$196.84	$196.85	$196.80
Purchase #2	$211.94	8.823%	$230.6395	$230.64	$230.65	$230.60
Purchase #3	$105.81	5.513%	$111.6433	$111.64	$111.65	$111.60
Purchase #4	$90.63	6.869%	$96.8554	$96.86	$96.85	$96.90
Purchase #5	$101.44	12.210%	$113.8258	$113.83	$113.85	$113.80
Purchase #6	$122.25	6.850%	$130.6241	$130.62	$130.60	$130.60
Purchase #7	$37.55	12.462%	$42.2295	$42.23	$42.25	$42.20
7 purchase totals =	$847.58		$922.6574	$922.66	$922.70	$922.50