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	$64.68	12.117%	$72.5173	$72.52	$72.50	$72.50
Purchase #2	$238.64	7.157%	$255.7195	$255.72	$255.70	$255.70
Purchase #3	$198.94	4.288%	$207.4705	$207.47	$207.45	$207.50
Purchase #4	$47.95	13.359%	$54.3556	$54.36	$54.35	$54.40
Purchase #5	$212.40	13.116%	$240.2584	$240.26	$240.25	$240.30
Purchase #6	$33.66	11.549%	$37.5474	$37.55	$37.55	$37.50
Purchase #7	$208.80	10.329%	$230.367	$230.37	$230.35	$230.40
7 purchase totals =	$1,005.07		$1,098.2357	$1,098.25	$1,098.15	$1,098.30