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	$204.50	8.811%	$222.5185	$222.52	$222.50	$222.50
Purchase #2	$230.52	3.483%	$238.549	$238.55	$238.55	$238.50
Purchase #3	$23.51	6.286%	$24.9878	$24.99	$25.00	$25.00
Purchase #4	$230.45	6.669%	$245.8187	$245.82	$245.80	$245.80
Purchase #5	$217.98	9.306%	$238.2652	$238.27	$238.25	$238.30
Purchase #6	$37.76	6.623%	$40.2608	$40.26	$40.25	$40.30
Purchase #7	$11.38	10.667%	$12.5939	$12.59	$12.60	$12.60
7 purchase totals =	$956.10		$1,022.9939	$1,023.00	$1,022.95	$1,023.00