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	$11.80	5.655%	$12.4673	$12.47	$12.45	$12.50
Purchase #2	$244.35	7.604%	$262.9304	$262.93	$262.95	$262.90
Purchase #3	$128.79	9.562%	$141.1049	$141.10	$141.10	$141.10
Purchase #4	$144.40	5.861%	$152.8633	$152.86	$152.85	$152.90
Purchase #5	$246.94	13.241%	$279.6373	$279.64	$279.65	$279.60
Purchase #6	$151.43	4.649%	$158.47	$158.47	$158.45	$158.50
Purchase #7	$54.67	4.671%	$57.2236	$57.22	$57.20	$57.20
7 purchase totals =	$982.38		$1,064.6968	$1,064.69	$1,064.65	$1,064.70