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	$123.94	6.468%	$131.9564	$131.96	$131.95	$132.00
Purchase #2	$73.31	13.365%	$83.1079	$83.11	$83.10	$83.10
Purchase #3	$129.77	9.671%	$142.3201	$142.32	$142.30	$142.30
Purchase #4	$159.65	10.659%	$176.6671	$176.67	$176.65	$176.70
Purchase #5	$226.68	12.496%	$255.0059	$255.01	$255.00	$255.00
Purchase #6	$197.54	5.366%	$208.14	$208.14	$208.15	$208.10
Purchase #7	$167.50	6.636%	$178.6153	$178.62	$178.60	$178.60
7 purchase totals =	$1,078.39		$1,175.8127	$1,175.83	$1,175.75	$1,175.80