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	$61.54	4.256%	$64.1591	$64.16	$64.15	$64.20
Purchase #2	$95.54	10.514%	$105.5851	$105.59	$105.60	$105.60
Purchase #3	$183.66	8.396%	$199.0801	$199.08	$199.10	$199.10
Purchase #4	$13.75	3.180%	$14.1873	$14.19	$14.20	$14.20
Purchase #5	$212.66	7.634%	$228.8945	$228.89	$228.90	$228.90
Purchase #6	$24.70	3.382%	$25.5354	$25.54	$25.55	$25.50
Purchase #7	$100.87	10.348%	$111.308	$111.31	$111.30	$111.30
7 purchase totals =	$692.72		$748.7495	$748.76	$748.80	$748.80