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	$223.64	7.561%	$240.5494	$240.55	$240.55	$240.50
Purchase #2	$48.32	10.614%	$53.4487	$53.45	$53.45	$53.40
Purchase #3	$182.87	8.501%	$198.4158	$198.42	$198.40	$198.40
Purchase #4	$180.69	3.536%	$187.0792	$187.08	$187.10	$187.10
Purchase #5	$64.65	12.409%	$72.6724	$72.67	$72.65	$72.70
Purchase #6	$230.88	10.459%	$255.0277	$255.03	$255.05	$255.00
Purchase #7	$241.68	7.521%	$259.8568	$259.86	$259.85	$259.90
7 purchase totals =	$1,172.73		$1,267.0500	$1,267.06	$1,267.05	$1,267.00