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	$242.90	10.291%	$267.8968	$267.90	$267.90	$267.90
Purchase #2	$230.35	4.537%	$240.801	$240.80	$240.80	$240.80
Purchase #3	$113.90	5.801%	$120.5073	$120.51	$120.50	$120.50
Purchase #4	$154.36	5.167%	$162.3358	$162.34	$162.35	$162.30
Purchase #5	$31.34	13.724%	$35.6411	$35.64	$35.65	$35.60
Purchase #6	$157.39	13.147%	$178.0821	$178.08	$178.10	$178.10
Purchase #7	$52.51	12.505%	$59.0764	$59.08	$59.10	$59.10
7 purchase totals =	$982.75		$1,064.3405	$1,064.35	$1,064.40	$1,064.30