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	$95.50	13.126%	$108.0353	$108.04	$108.05	$108.00
Purchase #2	$80.61	6.696%	$86.0076	$86.01	$86.00	$86.00
Purchase #3	$8.56	12.222%	$9.6062	$9.61	$9.60	$9.60
Purchase #4	$95.45	8.648%	$103.7045	$103.70	$103.70	$103.70
Purchase #5	$19.83	7.450%	$21.3073	$21.31	$21.30	$21.30
Purchase #6	$94.78	10.820%	$105.0352	$105.04	$105.05	$105.00
Purchase #7	$62.84	3.450%	$65.008	$65.01	$65.00	$65.00
7 purchase totals =	$457.57		$498.7041	$498.72	$498.70	$498.60