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	$102.25	9.589%	$112.0548	$112.05	$112.05	$112.10
Purchase #2	$249.68	13.141%	$282.4904	$282.49	$282.50	$282.50
Purchase #3	$79.61	12.160%	$89.2906	$89.29	$89.30	$89.30
Purchase #4	$56.84	10.126%	$62.5956	$62.60	$62.60	$62.60
Purchase #5	$34.74	9.410%	$38.009	$38.01	$38.00	$38.00
Purchase #6	$218.87	8.528%	$237.5352	$237.54	$237.55	$237.50
Purchase #7	$249.57	4.518%	$260.8456	$260.85	$260.85	$260.80
7 purchase totals =	$991.56		$1,082.8212	$1,082.83	$1,082.85	$1,082.80