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	$48.58	13.282%	$55.0324	$55.03	$55.05	$55.00
Purchase #2	$92.32	4.648%	$96.611	$96.61	$96.60	$96.60
Purchase #3	$81.60	9.123%	$89.0444	$89.04	$89.05	$89.00
Purchase #4	$116.65	4.849%	$122.3064	$122.31	$122.30	$122.30
Purchase #5	$176.59	10.192%	$194.5881	$194.59	$194.60	$194.60
Purchase #6	$209.73	13.769%	$238.6077	$238.61	$238.60	$238.60
Purchase #7	$224.42	7.614%	$241.5073	$241.51	$241.50	$241.50
7 purchase totals =	$949.89		$1,037.6973	$1,037.70	$1,037.70	$1,037.60