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	$208.25	10.573%	$230.2683	$230.27	$230.25	$230.30
Purchase #2	$146.71	13.478%	$166.4836	$166.48	$166.50	$166.50
Purchase #3	$187.75	4.750%	$196.6681	$196.67	$196.65	$196.70
Purchase #4	$111.52	10.671%	$123.4203	$123.42	$123.40	$123.40
Purchase #5	$225.54	4.187%	$234.9834	$234.98	$235.00	$235.00
Purchase #6	$113.47	11.465%	$126.4793	$126.48	$126.50	$126.50
Purchase #7	$165.36	11.759%	$184.8047	$184.80	$184.80	$184.80
7 purchase totals =	$1,158.60		$1,263.1077	$1,263.10	$1,263.10	$1,263.20