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	$245.72	5.324%	$258.8021	$258.80	$258.80	$258.80
Purchase #2	$23.58	6.694%	$25.1584	$25.16	$25.15	$25.20
Purchase #3	$244.59	6.366%	$260.1606	$260.16	$260.15	$260.20
Purchase #4	$78.66	13.401%	$89.2012	$89.20	$89.20	$89.20
Purchase #5	$12.32	3.169%	$12.7104	$12.71	$12.70	$12.70
Purchase #6	$180.90	5.253%	$190.4027	$190.40	$190.40	$190.40
Purchase #7	$92.86	12.320%	$104.3004	$104.30	$104.30	$104.30
7 purchase totals =	$878.63		$940.7358	$940.73	$940.70	$940.80