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	$58.28	7.369%	$62.5747	$62.57	$62.55	$62.60
Purchase #2	$120.95	7.819%	$130.4071	$130.41	$130.40	$130.40
Purchase #3	$240.60	7.433%	$258.4838	$258.48	$258.50	$258.50
Purchase #4	$186.77	3.241%	$192.8232	$192.82	$192.80	$192.80
Purchase #5	$99.95	11.724%	$111.6681	$111.67	$111.65	$111.70
Purchase #6	$42.86	9.515%	$46.9381	$46.94	$46.95	$46.90
Purchase #7	$111.64	4.301%	$116.4416	$116.44	$116.45	$116.40
7 purchase totals =	$861.05		$919.3366	$919.33	$919.30	$919.30