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	$185.64	13.495%	$210.6921	$210.69	$210.70	$210.70
Purchase #2	$27.37	13.235%	$30.9924	$30.99	$31.00	$31.00
Purchase #3	$55.80	6.443%	$59.3952	$59.40	$59.40	$59.40
Purchase #4	$106.91	5.227%	$112.4982	$112.50	$112.50	$112.50
Purchase #5	$37.76	3.638%	$39.1337	$39.13	$39.15	$39.10
Purchase #6	$133.81	7.549%	$143.9113	$143.91	$143.90	$143.90
Purchase #7	$12.98	4.589%	$13.5757	$13.58	$13.60	$13.60
7 purchase totals =	$560.27		$610.1986	$610.20	$610.25	$610.20