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	$240.94	10.316%	$265.7954	$265.80	$265.80	$265.80
Purchase #2	$61.68	5.150%	$64.8565	$64.86	$64.85	$64.90
Purchase #3	$210.71	9.210%	$230.1164	$230.12	$230.10	$230.10
Purchase #4	$200.47	3.824%	$208.136	$208.14	$208.15	$208.10
Purchase #5	$6.51	4.808%	$6.823	$6.82	$6.80	$6.80
Purchase #6	$81.79	10.602%	$90.4614	$90.46	$90.45	$90.50
Purchase #7	$134.54	8.700%	$146.245	$146.25	$146.25	$146.20
7 purchase totals =	$936.64		$1,012.4337	$1,012.45	$1,012.40	$1,012.40