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	$136.33	4.541%	$142.5207	$142.52	$142.50	$142.50
Purchase #2	$11.83	12.508%	$13.3097	$13.31	$13.30	$13.30
Purchase #3	$16.87	4.294%	$17.5944	$17.59	$17.60	$17.60
Purchase #4	$50.90	8.173%	$55.0601	$55.06	$55.05	$55.10
Purchase #5	$106.67	7.367%	$114.5284	$114.53	$114.55	$114.50
Purchase #6	$96.98	10.829%	$107.482	$107.48	$107.50	$107.50
Purchase #7	$113.46	8.798%	$123.4422	$123.44	$123.45	$123.40
7 purchase totals =	$533.04		$573.9375	$573.93	$573.95	$573.90