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	$155.96	4.281%	$162.6366	$162.64	$162.65	$162.60
Purchase #2	$230.43	3.208%	$237.8222	$237.82	$237.80	$237.80
Purchase #3	$83.38	13.480%	$94.6196	$94.62	$94.60	$94.60
Purchase #4	$36.51	5.418%	$38.4881	$38.49	$38.50	$38.50
Purchase #5	$209.43	10.682%	$231.8013	$231.80	$231.80	$231.80
Purchase #6	$66.32	12.217%	$74.4223	$74.42	$74.40	$74.40
Purchase #7	$155.79	6.231%	$165.4973	$165.50	$165.50	$165.50
7 purchase totals =	$937.82		$1,005.2874	$1,005.29	$1,005.25	$1,005.20