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	$56.62	13.388%	$64.2003	$64.20	$64.20	$64.20
Purchase #2	$192.33	12.488%	$216.3482	$216.35	$216.35	$216.30
Purchase #3	$173.56	13.236%	$196.5324	$196.53	$196.55	$196.50
Purchase #4	$70.40	10.320%	$77.6653	$77.67	$77.65	$77.70
Purchase #5	$233.38	13.746%	$265.4604	$265.46	$265.45	$265.50
Purchase #6	$68.38	7.416%	$73.4511	$73.45	$73.45	$73.50
Purchase #7	$211.86	10.258%	$233.5926	$233.59	$233.60	$233.60
7 purchase totals =	$1,006.53		$1,127.2503	$1,127.25	$1,127.25	$1,127.30