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	$102.82	8.725%	$111.791	$111.79	$111.80	$111.80
Purchase #2	$74.61	5.345%	$78.5979	$78.60	$78.60	$78.60
Purchase #3	$37.51	5.513%	$39.5779	$39.58	$39.60	$39.60
Purchase #4	$167.82	8.649%	$182.3348	$182.33	$182.35	$182.30
Purchase #5	$235.52	9.120%	$256.9994	$257.00	$257.00	$257.00
Purchase #6	$211.98	6.384%	$225.5128	$225.51	$225.50	$225.50
Purchase #7	$175.77	5.467%	$185.3793	$185.38	$185.40	$185.40
7 purchase totals =	$1,006.03		$1,080.1931	$1,080.19	$1,080.25	$1,080.20