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	$52.87	12.556%	$59.5084	$59.51	$59.50	$59.50
Purchase #2	$215.41	6.755%	$229.9609	$229.96	$229.95	$230.00
Purchase #3	$150.40	11.626%	$167.8855	$167.89	$167.90	$167.90
Purchase #4	$121.38	3.491%	$125.6174	$125.62	$125.60	$125.60
Purchase #5	$214.90	10.411%	$237.2732	$237.27	$237.25	$237.30
Purchase #6	$224.89	6.757%	$240.0858	$240.09	$240.10	$240.10
Purchase #7	$158.85	13.853%	$180.8555	$180.86	$180.85	$180.90
7 purchase totals =	$1,138.70		$1,241.1867	$1,241.20	$1,241.15	$1,241.30