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	$209.75	10.449%	$231.6668	$231.67	$231.65	$231.70
Purchase #2	$37.52	6.222%	$39.8545	$39.85	$39.85	$39.90
Purchase #3	$241.45	6.659%	$257.5282	$257.53	$257.55	$257.50
Purchase #4	$214.31	10.279%	$236.3389	$236.34	$236.35	$236.30
Purchase #5	$235.44	9.652%	$258.1647	$258.16	$258.15	$258.20
Purchase #6	$70.52	3.435%	$72.9424	$72.94	$72.95	$72.90
Purchase #7	$76.43	12.307%	$85.8362	$85.84	$85.85	$85.80
7 purchase totals =	$1,085.42		$1,182.3317	$1,182.33	$1,182.35	$1,182.30