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	$94.34	3.610%	$97.7457	$97.75	$97.75	$97.70
Purchase #2	$132.77	8.851%	$144.5215	$144.52	$144.50	$144.50
Purchase #3	$221.32	9.173%	$241.6217	$241.62	$241.60	$241.60
Purchase #4	$111.85	4.152%	$116.494	$116.49	$116.50	$116.50
Purchase #5	$116.41	10.725%	$128.895	$128.90	$128.90	$128.90
Purchase #6	$111.85	7.110%	$119.8025	$119.80	$119.80	$119.80
Purchase #7	$112.68	9.596%	$123.4928	$123.49	$123.50	$123.50
7 purchase totals =	$901.22		$972.5732	$972.57	$972.55	$972.50