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	$242.95	6.806%	$259.4852	$259.49	$259.50	$259.50
Purchase #2	$62.82	4.570%	$65.6909	$65.69	$65.70	$65.70
Purchase #3	$121.44	8.260%	$131.4709	$131.47	$131.45	$131.50
Purchase #4	$36.58	3.710%	$37.9371	$37.94	$37.95	$37.90
Purchase #5	$235.62	3.815%	$244.6089	$244.61	$244.60	$244.60
Purchase #6	$145.54	5.658%	$153.7747	$153.77	$153.75	$153.80
Purchase #7	$163.83	6.224%	$174.0268	$174.03	$174.05	$174.00
7 purchase totals =	$1,008.78		$1,066.9945	$1,067.00	$1,067.00	$1,067.00