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	$82.91	10.353%	$91.4937	$91.49	$91.50	$91.50
Purchase #2	$95.92	10.381%	$105.8775	$105.88	$105.90	$105.90
Purchase #3	$47.80	6.355%	$50.8377	$50.84	$50.85	$50.80
Purchase #4	$87.67	11.351%	$97.6214	$97.62	$97.60	$97.60
Purchase #5	$141.32	3.216%	$145.8649	$145.86	$145.85	$145.90
Purchase #6	$105.65	9.344%	$115.5219	$115.52	$115.50	$115.50
Purchase #7	$19.98	8.586%	$21.6955	$21.70	$21.70	$21.70
7 purchase totals =	$581.25		$628.9126	$628.91	$628.90	$628.90