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	$54.92	12.646%	$61.8652	$61.87	$61.85	$61.90
Purchase #2	$70.33	7.393%	$75.5295	$75.53	$75.55	$75.50
Purchase #3	$165.77	5.525%	$174.9288	$174.93	$174.95	$174.90
Purchase #4	$84.51	7.226%	$90.6167	$90.62	$90.60	$90.60
Purchase #5	$11.51	8.804%	$12.5233	$12.52	$12.50	$12.50
Purchase #6	$30.36	4.820%	$31.8234	$31.82	$31.80	$31.80
Purchase #7	$165.53	9.735%	$181.6443	$181.64	$181.65	$181.60
7 purchase totals =	$582.93		$628.9312	$628.93	$628.90	$628.80