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	$9.72	8.536%	$10.5497	$10.55	$10.55	$10.50
Purchase #2	$62.73	7.625%	$67.5132	$67.51	$67.50	$67.50
Purchase #3	$217.27	5.233%	$228.6397	$228.64	$228.65	$228.60
Purchase #4	$236.86	12.566%	$266.6238	$266.62	$266.60	$266.60
Purchase #5	$250.80	10.771%	$277.8137	$277.81	$277.80	$277.80
Purchase #6	$204.37	9.521%	$223.8281	$223.83	$223.85	$223.80
Purchase #7	$42.34	7.177%	$45.3787	$45.38	$45.40	$45.40
7 purchase totals =	$1,024.09		$1,120.3469	$1,120.34	$1,120.35	$1,120.20