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	$200.84	6.291%	$213.4748	$213.47	$213.45	$213.50
Purchase #2	$89.82	9.220%	$98.1014	$98.10	$98.10	$98.10
Purchase #3	$173.72	13.258%	$196.7518	$196.75	$196.75	$196.80
Purchase #4	$55.69	12.400%	$62.5956	$62.60	$62.60	$62.60
Purchase #5	$78.90	9.509%	$86.4026	$86.40	$86.40	$86.40
Purchase #6	$156.25	10.784%	$173.1	$173.10	$173.10	$173.10
Purchase #7	$52.55	5.585%	$55.4849	$55.48	$55.50	$55.50
7 purchase totals =	$807.77		$885.9111	$885.90	$885.90	$886.00