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	$142.51	4.340%	$148.6949	$148.69	$148.70	$148.70
Purchase #2	$23.36	11.577%	$26.0644	$26.06	$26.05	$26.10
Purchase #3	$90.29	5.639%	$95.3815	$95.38	$95.40	$95.40
Purchase #4	$198.30	8.224%	$214.6082	$214.61	$214.60	$214.60
Purchase #5	$226.46	13.373%	$256.7445	$256.74	$256.75	$256.70
Purchase #6	$93.77	12.496%	$105.4875	$105.49	$105.50	$105.50
Purchase #7	$199.70	11.583%	$222.8313	$222.83	$222.85	$222.80
7 purchase totals =	$974.39		$1,069.8123	$1,069.80	$1,069.85	$1,069.80