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	$233.96	9.255%	$255.613	$255.61	$255.60	$255.60
Purchase #2	$45.41	4.830%	$47.6033	$47.60	$47.60	$47.60
Purchase #3	$165.81	10.313%	$182.91	$182.91	$182.90	$182.90
Purchase #4	$37.26	9.776%	$40.9025	$40.90	$40.90	$40.90
Purchase #5	$14.47	3.628%	$14.995	$15.00	$15.00	$15.00
Purchase #6	$234.37	6.207%	$248.9173	$248.92	$248.90	$248.90
Purchase #7	$6.43	4.480%	$6.7181	$6.72	$6.70	$6.70
7 purchase totals =	$737.71		$797.6592	$797.66	$797.60	$797.60