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	$91.83	13.748%	$104.4548	$104.45	$104.45	$104.50
Purchase #2	$41.93	7.737%	$45.1741	$45.17	$45.15	$45.20
Purchase #3	$224.35	6.652%	$239.2738	$239.27	$239.25	$239.30
Purchase #4	$105.31	6.134%	$111.7697	$111.77	$111.75	$111.80
Purchase #5	$180.84	9.781%	$198.528	$198.53	$198.55	$198.50
Purchase #6	$134.70	13.617%	$153.0421	$153.04	$153.05	$153.00
Purchase #7	$53.47	10.452%	$59.0587	$59.06	$59.05	$59.10
7 purchase totals =	$832.43		$911.3012	$911.29	$911.25	$911.40