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	$74.31	11.160%	$82.603	$82.60	$82.60	$82.60
Purchase #2	$130.48	3.359%	$134.8628	$134.86	$134.85	$134.90
Purchase #3	$226.59	13.587%	$257.3768	$257.38	$257.40	$257.40
Purchase #4	$54.77	11.258%	$60.936	$60.94	$60.95	$60.90
Purchase #5	$114.95	7.524%	$123.5988	$123.60	$123.60	$123.60
Purchase #6	$235.94	8.235%	$255.3697	$255.37	$255.35	$255.40
Purchase #7	$137.43	13.266%	$155.6615	$155.66	$155.65	$155.70
7 purchase totals =	$974.47		$1,070.4086	$1,070.41	$1,070.40	$1,070.50