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	$124.46	5.629%	$131.4659	$131.47	$131.45	$131.50
Purchase #2	$12.67	3.605%	$13.1268	$13.13	$13.15	$13.10
Purchase #3	$84.25	9.797%	$92.504	$92.50	$92.50	$92.50
Purchase #4	$77.91	13.501%	$88.4286	$88.43	$88.45	$88.40
Purchase #5	$68.28	9.265%	$74.6061	$74.61	$74.60	$74.60
Purchase #6	$238.83	6.493%	$254.3372	$254.34	$254.35	$254.30
Purchase #7	$148.58	13.288%	$168.3233	$168.32	$168.30	$168.30
7 purchase totals =	$754.98		$822.7919	$822.80	$822.80	$822.70