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	$95.82	4.177%	$99.8224	$99.82	$99.80	$99.80
Purchase #2	$97.94	3.401%	$101.2709	$101.27	$101.25	$101.30
Purchase #3	$57.52	4.203%	$59.9376	$59.94	$59.95	$59.90
Purchase #4	$43.70	4.243%	$45.5542	$45.55	$45.55	$45.60
Purchase #5	$194.74	12.653%	$219.3805	$219.38	$219.40	$219.40
Purchase #6	$111.67	5.179%	$117.4534	$117.45	$117.45	$117.50
Purchase #7	$75.68	11.593%	$84.4536	$84.45	$84.45	$84.50
7 purchase totals =	$677.07		$727.8726	$727.86	$727.85	$728.00