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	$69.43	4.243%	$72.3759	$72.38	$72.40	$72.40
Purchase #2	$68.83	5.351%	$72.5131	$72.51	$72.50	$72.50
Purchase #3	$132.42	8.528%	$143.7128	$143.71	$143.70	$143.70
Purchase #4	$150.62	11.338%	$167.6973	$167.70	$167.70	$167.70
Purchase #5	$136.94	3.859%	$142.2245	$142.22	$142.20	$142.20
Purchase #6	$88.30	3.778%	$91.636	$91.64	$91.65	$91.60
Purchase #7	$35.91	6.176%	$38.1278	$38.13	$38.15	$38.10
7 purchase totals =	$682.45		$728.2874	$728.29	$728.30	$728.20