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	$199.45	12.794%	$224.9676	$224.97	$224.95	$225.00
Purchase #2	$38.64	6.301%	$41.0747	$41.07	$41.05	$41.10
Purchase #3	$53.92	11.189%	$59.9531	$59.95	$59.95	$60.00
Purchase #4	$42.46	8.139%	$45.9158	$45.92	$45.90	$45.90
Purchase #5	$185.92	3.190%	$191.8508	$191.85	$191.85	$191.90
Purchase #6	$111.38	6.285%	$118.3802	$118.38	$118.40	$118.40
Purchase #7	$56.52	10.535%	$62.4744	$62.47	$62.45	$62.50
7 purchase totals =	$688.29		$744.6166	$744.61	$744.55	$744.80