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	$208.41	12.112%	$233.6526	$233.65	$233.65	$233.70
Purchase #2	$196.57	9.621%	$215.482	$215.48	$215.50	$215.50
Purchase #3	$150.42	9.691%	$164.9972	$165.00	$165.00	$165.00
Purchase #4	$98.41	10.139%	$108.3878	$108.39	$108.40	$108.40
Purchase #5	$220.62	3.171%	$227.6159	$227.62	$227.60	$227.60
Purchase #6	$59.45	5.506%	$62.7233	$62.72	$62.70	$62.70
Purchase #7	$144.47	10.658%	$159.8676	$159.87	$159.85	$159.90
7 purchase totals =	$1,078.35		$1,172.7264	$1,172.73	$1,172.70	$1,172.80