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	$43.40	6.828%	$46.3634	$46.36	$46.35	$46.40
Purchase #2	$43.43	5.481%	$45.8104	$45.81	$45.80	$45.80
Purchase #3	$42.27	3.457%	$43.7313	$43.73	$43.75	$43.70
Purchase #4	$95.80	11.284%	$106.6101	$106.61	$106.60	$106.60
Purchase #5	$100.78	12.437%	$113.314	$113.31	$113.30	$113.30
Purchase #6	$154.71	12.240%	$173.6465	$173.65	$173.65	$173.60
Purchase #7	$233.53	9.340%	$255.3417	$255.34	$255.35	$255.30
7 purchase totals =	$713.92		$784.8174	$784.81	$784.80	$784.70