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	$148.49	8.159%	$160.6053	$160.61	$160.60	$160.60
Purchase #2	$200.89	8.546%	$218.0581	$218.06	$218.05	$218.10
Purchase #3	$111.42	5.386%	$117.4211	$117.42	$117.40	$117.40
Purchase #4	$58.77	4.639%	$61.4963	$61.50	$61.50	$61.50
Purchase #5	$26.99	9.670%	$29.5999	$29.60	$29.60	$29.60
Purchase #6	$59.89	4.392%	$62.5204	$62.52	$62.50	$62.50
Purchase #7	$183.70	13.293%	$208.1192	$208.12	$208.10	$208.10
7 purchase totals =	$790.15		$857.8203	$857.83	$857.75	$857.80