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	$102.97	6.181%	$109.3346	$109.33	$109.35	$109.30
Purchase #2	$68.86	8.584%	$74.7709	$74.77	$74.75	$74.80
Purchase #3	$44.86	10.563%	$49.5986	$49.60	$49.60	$49.60
Purchase #4	$184.89	8.409%	$200.4374	$200.44	$200.45	$200.40
Purchase #5	$86.70	3.190%	$89.4657	$89.47	$89.45	$89.50
Purchase #6	$242.52	4.126%	$252.5264	$252.53	$252.55	$252.50
Purchase #7	$238.69	12.776%	$269.185	$269.19	$269.20	$269.20
7 purchase totals =	$969.49		$1,045.3186	$1,045.33	$1,045.35	$1,045.30