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	$217.77	5.629%	$230.0283	$230.03	$230.05	$230.00
Purchase #2	$23.72	3.708%	$24.5995	$24.60	$24.60	$24.60
Purchase #3	$218.59	12.171%	$245.1946	$245.19	$245.20	$245.20
Purchase #4	$49.80	3.759%	$51.672	$51.67	$51.65	$51.70
Purchase #5	$24.27	5.333%	$25.5643	$25.56	$25.55	$25.60
Purchase #6	$242.62	5.737%	$256.5391	$256.54	$256.55	$256.50
Purchase #7	$241.28	10.609%	$266.8774	$266.88	$266.90	$266.90
7 purchase totals =	$1,018.05		$1,100.4752	$1,100.47	$1,100.50	$1,100.50