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	$235.80	4.675%	$246.8237	$246.82	$246.80	$246.80
Purchase #2	$105.51	3.775%	$109.493	$109.49	$109.50	$109.50
Purchase #3	$226.77	6.677%	$241.9114	$241.91	$241.90	$241.90
Purchase #4	$58.40	6.178%	$62.008	$62.01	$62.00	$62.00
Purchase #5	$240.47	7.641%	$258.8443	$258.84	$258.85	$258.80
Purchase #6	$67.72	7.306%	$72.6676	$72.67	$72.65	$72.70
Purchase #7	$63.44	9.753%	$69.6273	$69.63	$69.65	$69.60
7 purchase totals =	$998.11		$1,061.3753	$1,061.37	$1,061.35	$1,061.30