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	$10.79	4.591%	$11.2854	$11.29	$11.30	$11.30
Purchase #2	$162.54	4.242%	$169.4349	$169.43	$169.45	$169.40
Purchase #3	$48.88	11.268%	$54.3878	$54.39	$54.40	$54.40
Purchase #4	$53.58	7.413%	$57.5519	$57.55	$57.55	$57.60
Purchase #5	$146.26	8.577%	$158.8047	$158.80	$158.80	$158.80
Purchase #6	$41.93	5.638%	$44.294	$44.29	$44.30	$44.30
Purchase #7	$89.83	9.705%	$98.548	$98.55	$98.55	$98.50
7 purchase totals =	$553.81		$594.3067	$594.30	$594.35	$594.30