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	$12.41	9.734%	$13.618	$13.62	$13.60	$13.60
Purchase #2	$216.39	6.611%	$230.6955	$230.70	$230.70	$230.70
Purchase #3	$238.85	5.354%	$251.638	$251.64	$251.65	$251.60
Purchase #4	$115.95	6.325%	$123.2838	$123.28	$123.30	$123.30
Purchase #5	$197.96	13.390%	$224.4668	$224.47	$224.45	$224.50
Purchase #6	$215.55	3.780%	$223.6978	$223.70	$223.70	$223.70
Purchase #7	$28.97	13.565%	$32.8998	$32.90	$32.90	$32.90
7 purchase totals =	$1,026.08		$1,100.2997	$1,100.31	$1,100.30	$1,100.30