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	$149.99	13.392%	$170.0767	$170.08	$170.10	$170.10
Purchase #2	$95.41	10.670%	$105.5902	$105.59	$105.60	$105.60
Purchase #3	$113.82	12.850%	$128.4459	$128.45	$128.45	$128.40
Purchase #4	$208.49	6.563%	$222.1732	$222.17	$222.15	$222.20
Purchase #5	$247.52	12.870%	$279.3758	$279.38	$279.40	$279.40
Purchase #6	$10.27	13.457%	$11.652	$11.65	$11.65	$11.70
Purchase #7	$100.36	5.239%	$105.6179	$105.62	$105.60	$105.60
7 purchase totals =	$925.86		$1,022.9317	$1,022.94	$1,022.95	$1,023.00